diff --git a/ANNOUNCE b/ANNOUNCE
index 366ace5..bca4250 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.23 - June 9, 2016
+Libpng 1.6.24 - August 4, 2016
 
 This is a public release of libpng, intended for use in production codes.
 
@@ -7,38 +7,78 @@
 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script
 
-   libpng-1.6.23.tar.xz (LZMA-compressed, recommended)
-   libpng-1.6.23.tar.gz
+   libpng-1.6.24.tar.xz (LZMA-compressed, recommended)
+   libpng-1.6.24.tar.gz
 
 Source files with CRLF line endings (for Windows), without the
 "configure" script
 
-   lpng1623.7z  (LZMA-compressed, recommended)
-   lpng1623.zip
+   lpng1624.7z  (LZMA-compressed, recommended)
+   lpng1624.zip
 
 Other information:
 
-   libpng-1.6.23-README.txt
-   libpng-1.6.23-LICENSE.txt
-   libpng-1.6.23-*.asc (armored detached GPG signatures)
+   libpng-1.6.24-README.txt
+   libpng-1.6.24-LICENSE.txt
+   libpng-1.6.24-*.asc (armored detached GPG signatures)
 
-Changes since the last public release (1.6.22):
-
-  Stop a potential memory leak in png_set_tRNS() (Bug report by Ted Ying).
-  Fixed the progressive reader to handle empty first IDAT chunk properly
-    (patch by Timothy Nikkel).  This bug was introduced in libpng-1.6.0 and
-    only affected the libpng16 branch.
-  Added tests in pngvalid.c to check zero-length IDAT chunks in various
-    positions.  Fixed the sequential reader to handle these more robustly
-    (John Bowler).
-  Corrected progressive read input buffer in pngvalid.c. The previous version
-    the code invariably passed just one byte at a time to libpng.  The intent
-    was to pass a random number of bytes in the range 0..511.
-  Moved sse2 prototype from pngpriv.h to contrib/intel/intel_sse.patch.
-  Added missing ")" in pngerror.c (Matt Sarrett).
-  Fixed undefined behavior in png_push_save_buffer(). Do not call
-    memcpy() with a null source, even if count is zero (Leon Scroggins III).
-  Fixed bad link to RFC2083 in png.5 (Nikola Forro).
+Changes since the last public release (1.6.23):
+  Avoid potential overflow of the PNG_IMAGE_SIZE macro.  This macro
+    is not used within libpng, but is used in some of the examples.
+  Correct filter heuristic overflow handling. This was broken when the
+    write filter code was moved out-of-line; if there is a single filter and
+    the heuristic sum overflows the calculation of the filtered line is not
+    completed.  In versions prior to 1.6 the code was duplicated in-line
+    and the check not performed, so the filter operation completed; however,
+    in the multi-filter case where the sum is performed the 'none' filter would
+    be selected if all the sums overflowed, even if it wasn't in the filter
+    list.  The fix to the first problem is simply to provide PNG_SIZE_MAX as
+    the current lmins sum value; this means the sum can never exceed it and
+    overflows silently.  A reasonable compiler that does choose to inline
+    the code will simply eliminate the sum check.
+  The fix to the second problem is to use high precision arithmetic (this is
+    implemented in 1.7), however a simple safe fix here is to chose the lowest
+    numbered filter in the list from png_set_filter (this only works if the
+    first problem is also fixed) (John Bowler).
+  Use a more efficient absolute value calculation on SSE2 (Matthieu Darbois).
+  Fixed the case where PNG_IMAGE_BUFFER_SIZE can overflow in the application
+    as a result of the application using an increased 'row_stride'; previously
+    png_image_finish_read only checked for overflow on the base calculation of
+    components.  (I.e. it checked for overflow of a 32-bit number on the total
+    number of pixel components in the output format, not the possibly padded row
+    length and not the number of bytes, which for linear formats is twice the
+    number of components.)
+  MSVC does not like '-(unsigned)', so replaced it with 0U-(unsigned)
+  MSVC does not like (uInt) = -(unsigned) (i.e. as an initializer), unless
+    the conversion is explicitly invoked by a cast.
+  Put the SKIP definition in the correct place. It needs to come after the
+    png.h include (see all the other .c files in contrib/libtests) because it
+    depends on PNG_LIBPNG_VER.
+  Removed the three compile warning options from the individual project
+    files into the zlib.props globals.  It increases the warning level from 4
+    to All and adds a list of the warnings that need to be turned off.  This is
+    semi-documentary; the intent is to tell libpng users which warnings have
+    been examined and judged non-fixable at present.  The warning about
+    structure padding is fixable, but it would be a signficant change (moving
+    structure members around).
+  Optimized absolute value calculation in filter selection, similar to
+    code in the PAETH decoder in pngrutil.c. Build with PNG_USE_ABS to
+    use this.
+  Added pngcp to the build together with a pngcp.dfa configuration test.
+  Added high resolution timing to pngcp.
+  Added "Common linking failures" section to INSTALL.
+  Relocated misplaced #endif in png.c sRGB profile checking.
+  Fixed two Coverity issues in pngcp.c.
+  Avoid filter-selection heuristic sum calculations in cases where only one
+    filter is a candidate for selection. This trades off code size (added
+    private png_setup_*_row_only() functions) for speed.
+  Fixed some indentation to comply with our coding style.
+  Added contrib/tools/reindent.
+  Eliminated unnecessary tests of boolean png_isaligned() vs 0.
+  Conditionally compile SSE2 headers in contrib/intel/intel_sse.patch
+  Conditionally compile png_decompress_chunk().
+  Conditionally compile ARM_NEON headers in pngpriv.h
+  Updated contrib/intel/intel_sse.patch
 
 (subscription required; visit
 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
diff --git a/CHANGES b/CHANGES
index 0d6180f..d4f0c8b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5596,6 +5596,85 @@
 Version 1.6.23 [June 9, 2016]
   Fixed bad link to RFC2083 in png.5 (Nikola Forro).
 
+Version 1.6.24beta01 [June 11, 2016]
+  Avoid potential overflow of the PNG_IMAGE_SIZE macro.  This macro
+    is not used within libpng, but is used in some of the examples.
+
+Version 1.6.24beta02 [June 23, 2016]
+  Correct filter heuristic overflow handling. This was broken when the
+    write filter code was moved out-of-line; if there is a single filter and
+    the heuristic sum overflows the calculation of the filtered line is not
+    completed.  In versions prior to 1.6 the code was duplicated in-line
+    and the check not performed, so the filter operation completed; however,
+    in the multi-filter case where the sum is performed the 'none' filter would
+    be selected if all the sums overflowed, even if it wasn't in the filter
+    list.  The fix to the first problem is simply to provide PNG_SIZE_MAX as
+    the current lmins sum value; this means the sum can never exceed it and
+    overflows silently.  A reasonable compiler that does choose to inline
+    the code will simply eliminate the sum check.
+  The fix to the second problem is to use high precision arithmetic (this is
+    implemented in 1.7), however a simple safe fix here is to chose the lowest
+    numbered filter in the list from png_set_filter (this only works if the
+    first problem is also fixed) (John Bowler).
+  Use a more efficient absolute value calculation on SSE2 (Matthieu Darbois).
+  Fixed the case where PNG_IMAGE_BUFFER_SIZE can overflow in the application
+    as a result of the application using an increased 'row_stride'; previously
+    png_image_finish_read only checked for overflow on the base calculation of
+    components.  (I.e. it checked for overflow of a 32-bit number on the total
+    number of pixel components in the output format, not the possibly padded row
+    length and not the number of bytes, which for linear formats is twice the
+    number of components.)
+  MSVC does not like '-(unsigned)', so replaced it with 0U-(unsigned)
+  MSVC does not like (uInt) = -(unsigned) (i.e. as an initializer), unless
+    the conversion is explicitly invoked by a cast.
+  Put the SKIP definition in the correct place. It needs to come after the
+    png.h include (see all the other .c files in contrib/libtests) because it
+    depends on PNG_LIBPNG_VER.
+  Removed the three compile warning options from the individual project
+    files into the zlib.props globals.  It increases the warning level from 4
+    to All and adds a list of the warnings that need to be turned off.  This is
+    semi-documentary; the intent is to tell libpng users which warnings have
+    been examined and judged non-fixable at present.  The warning about
+    structure padding is fixable, but it would be a signficant change (moving
+    structure members around).
+
+Version 1.6.24beta03 [July 4, 2016]
+  Optimized absolute value calculation in filter selection, similar to
+    code in the PAETH decoder in pngrutil.c. Build with PNG_USE_ABS to
+    use this.
+  Added pngcp to the build together with a pngcp.dfa configuration test.
+  Added high resolution timing to pngcp.
+  Added "Common linking failures" section to INSTALL.
+  Relocated misplaced #endif in png.c sRGB profile checking.
+  Fixed two Coverity issues in pngcp.c.
+
+Version 1.6.24beta04 [July 8, 2016]
+  Avoid filter-selection heuristic sum calculations in cases where only one
+    filter is a candidate for selection. This trades off code size (added
+    private png_setup_*_row_only() functions) for speed.
+
+Version 1.6.24beta05 [July 13, 2016]
+  Fixed some indentation to comply with our coding style.
+  Added contrib/tools/reindent.
+
+Version 1.6.24beta06 [July 18, 2016]
+  Fixed more indentation to comply with our coding style.
+  Eliminated unnecessary tests of boolean png_isaligned() vs 0.
+
+Version 1.6.24rc01 [July 25, 2016]
+  No changes.
+
+Version 1.6.24rc02 [August 1, 2016]
+  Conditionally compile SSE2 headers in contrib/intel/intel_sse.patch
+  Conditionally compile png_decompress_chunk().
+
+Version 1.6.24rc03 [August 2, 2016]
+  Conditionally compile ARM_NEON headers in pngpriv.h
+  Updated contrib/intel/intel_sse.patch
+
+Version 1.6.24[August 4, 2016]
+  No changes.
+
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6eb3781..186b65a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -35,7 +35,7 @@
 
 set(PNGLIB_MAJOR 1)
 set(PNGLIB_MINOR 6)
-set(PNGLIB_RELEASE 23)
+set(PNGLIB_RELEASE 24)
 set(PNGLIB_NAME libpng${PNGLIB_MAJOR}${PNGLIB_MINOR})
 set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_RELEASE})
 
@@ -696,7 +696,7 @@
 # SET UP LINKS
 if(PNG_SHARED)
   set_target_properties(png PROPERTIES
-#   VERSION 16.${PNGLIB_RELEASE}.1.6.23
+#   VERSION 16.${PNGLIB_RELEASE}.1.6.24
     VERSION 16.${PNGLIB_RELEASE}.0
     SOVERSION 16
     CLEAN_DIRECT_OUTPUT 1)
diff --git a/INSTALL b/INSTALL
index ca651e4..eed4dc8 100644
--- a/INSTALL
+++ b/INSTALL
@@ -18,7 +18,8 @@
 XIII. Removing unwanted object code
  XIV. Changes to the build and configuration of libpng in libpng-1.5.x
   XV. Setjmp/longjmp issues
- XVI. Other sources of information about libpng
+ XVI. Common linking failures
+XVII. Other sources of information about libpng
 
 I. Simple installation
 
@@ -78,7 +79,7 @@
 Before installing libpng, you must first install zlib, if it
 is not already on your system.  zlib can usually be found
 wherever you got libpng; otherwise go to http://zlib.net.  You can place
-zlib in in the same directory as libpng or in another directory.
+zlib in the same directory as libpng or in another directory.
 
 If your system already has a preinstalled zlib you will still need
 to have access to the zlib.h and zconf.h include files that
@@ -118,8 +119,8 @@
 
 Your directory structure should look like this:
 
-   ..       (the parent directory)
-      libpng  (this directory)
+   .. (the parent directory)
+      libpng (this directory)
           INSTALL (this file)
           README
           *.h, *.c  => libpng source files
@@ -382,28 +383,20 @@
 with PNG_SETJMP_SUPPORTED defined, or with PNG_SIMPLIFIED_READ_SUPPORTED
 and PNG_SIMPLIFIED_WRITE_SUPPORTED undefined.
 
-XVI. Other sources of information about libpng:
+XVI. Common linking failures
+
+If your application fails to find libpng or zlib entries while linking:
+
+  Be sure "-lz" appears after "-lpng" on your linking command.
+
+  Be sure you have built libpng, zlib, and your application for the
+  same platform (e.g., 32-bit or 64-bit).
+
+  If you are using the vstudio project, observe the WARNING in
+  project/vstudio/README.txt.
+
+XVII. Other sources of information about libpng:
 
 Further information can be found in the README and libpng-manual.txt
 files, in the individual makefiles, in png.h, and the manual pages
 libpng.3 and png.5.
-
-Using the ./configure script -- 16 December 2002.
-=================================================
-
-The ./configure script should work compatibly with what scripts/makefile.*
-did, however there are some options you might need to add to configure
-explicitly, which previously was done semi-automatically (if you didn't edit
-scripts/makefile.* yourself, that is)
-
-CFLAGS="-Wall -O -funroll-loops \
--malign-loops=2 -malign-functions=2" ./configure --prefix=/usr/include \
---with-pkgconfigdir=/usr/lib/pkgconfig --includedir=/usr/include
-
-You can alternatively specify --includedir=/usr/include, /usr/local/include,
-/usr/include/libpng16, or whatever.
-
-If you find that the configure script is out-of-date or is not supporting
-your platform properly, try running autogen.sh to regenerate "configure",
-"Makefile.in", and the other configuration files. Then try configure again.
-
diff --git a/LICENSE b/LICENSE
index b7ad4b9..d20f39e 100644
--- a/LICENSE
+++ b/LICENSE
@@ -10,7 +10,7 @@
 
 This code is released under the libpng license.
 
-libpng versions 1.0.7, July 1, 2000 through 1.6.23, June 9, 2016 are
+libpng versions 1.0.7, July 1, 2000 through 1.6.24, August 4, 2016 are
 Copyright (c) 2000-2002, 2004, 2006-2016 Glenn Randers-Pehrson, are
 derived from libpng-1.0.6, and are distributed according to the same
 disclaimer and license as libpng-1.0.6 with the following individuals
@@ -127,4 +127,4 @@
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-June 9, 2016
+August 4, 2016
diff --git a/Makefile.am b/Makefile.am
index 7212951..39e9bde 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -18,7 +18,7 @@
 endif
 
 # Utilities - installed
-bin_PROGRAMS= pngfix png-fix-itxt
+bin_PROGRAMS= pngcp pngfix png-fix-itxt
 
 # This ensures that pnglibconf.h gets built at the start of 'make all' or
 # 'make check', but it does not add dependencies to the individual programs,
@@ -53,6 +53,9 @@
 
 png_fix_itxt_SOURCES = contrib/tools/png-fix-itxt.c
 
+pngcp_SOURCES = contrib/tools/pngcp.c
+pngcp_LDADD = libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@.la
+
 # Generally these are single line shell scripts to run a test with a particular
 # set of parameters:
 TESTS =\
@@ -230,6 +233,7 @@
 
 contrib/tools/makesRGB.o: pnglibconf.h
 contrib/tools/pngfix.o: pnglibconf.h
+contrib/tools/pngcp.o: pnglibconf.h
 
 # We must use -DPNG_NO_USE_READ_MACROS here even when the library may actually
 # be built with PNG_USE_READ_MACROS; this prevents the read macros from
diff --git a/README b/README
index 38e9a14..a8fba91 100644
--- a/README
+++ b/README
@@ -1,4 +1,4 @@
-README for libpng version 1.6.23 - June 9, 2016 (shared library 16.0)
+README for libpng version 1.6.24 - August 4, 2016 (shared library 16.0)
 See the note about version numbers near the top of png.h
 
 See INSTALL for instructions on how to install libpng.
diff --git a/TODO b/TODO
index 7263377..0b3b651 100644
--- a/TODO
+++ b/TODO
@@ -11,7 +11,6 @@
 Improved dithering.
 Multi-lingual error and warning message support.
 Complete sRGB transformation (presently it simply uses gamma=0.45455).
-Make profile checking optional via a png_set_something() call.
 Man pages for function calls.
 Better documentation.
 Better filter selection
diff --git a/arm/arm_init.c b/arm/arm_init.c
index 52c3f31..02df812 100644
--- a/arm/arm_init.c
+++ b/arm/arm_init.c
@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2014,2016 Glenn Randers-Pehrson
  * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.6.22 [June 9, 2016]
+ * Last changed in libpng 1.6.22 [May 26, 2016]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/arm/filter_neon_intrinsics.c b/arm/filter_neon_intrinsics.c
index be5ccc7..ea7e356 100644
--- a/arm/filter_neon_intrinsics.c
+++ b/arm/filter_neon_intrinsics.c
@@ -5,7 +5,7 @@
  * Written by James Yu <james.yu at linaro.org>, October 2013.
  * Based on filter_neon.S, written by Mans Rullgard, 2011.
  *
- * Last changed in libpng 1.6.22 [June 9, 2016]
+ * Last changed in libpng 1.6.22 [May 26, 2016]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/configure.ac b/configure.ac
index 82a4097..3a3d208 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,7 +1,7 @@
 # configure.ac
 
 # Copyright (c) 2004-2015 Glenn Randers-Pehrson
-# Last changed in libpng 1.6.22 [June 9, 2016]
+# Last changed in libpng 1.6.22 [May 26, 2016]
 
 # This code is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
@@ -25,7 +25,7 @@
 
 dnl Version number stuff here:
 
-AC_INIT([libpng],[1.6.23],[png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng],[1.6.24],[png-mng-implement@lists.sourceforge.net])
 AC_CONFIG_MACRO_DIR([scripts])
 
 # libpng does not follow GNU file name conventions (hence 'foreign')
@@ -36,7 +36,7 @@
 # 1.13 is required for parallel tests
 AM_INIT_AUTOMAKE([1.13 foreign dist-xz color-tests silent-rules subdir-objects])
 # The following line causes --disable-maintainer-mode to be the default to
-# configure, this is necessary because libpng distributions cannot rely on the
+# configure. This is necessary because libpng distributions cannot rely on the
 # time stamps of the autotools generated files being correct
 AM_MAINTAINER_MODE
 
@@ -46,10 +46,10 @@
 dnl AM_PREREQ([1.11.2])
 dnl stop configure from automagically running automake
 
-PNGLIB_VERSION=1.6.23
+PNGLIB_VERSION=1.6.24
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=6
-PNGLIB_RELEASE=23
+PNGLIB_RELEASE=24
 
 dnl End of version number stuff
 
@@ -67,7 +67,7 @@
 AC_PROG_LN_S
 AC_PROG_MAKE_SET
 
-dnl libtool/libtoolize; version 2.4.2 is the tested version, this or any
+dnl libtool/libtoolize; version 2.4.2 is the tested version. This or any
 dnl compatible later version may be used
 LT_INIT([win32-dll])
 LT_PREREQ([2.4.2])
diff --git a/contrib/conftest/pngcp.dfa b/contrib/conftest/pngcp.dfa
new file mode 100644
index 0000000..15a856e
--- /dev/null
+++ b/contrib/conftest/pngcp.dfa
@@ -0,0 +1,57 @@
+# pngcp.dfa
+#  Build time configuration of libpng
+#
+# Author: John Bowler
+# Copyright: (c) John Bowler, 2016
+# Usage rights:
+#  To the extent possible under law, the author has waived all copyright and
+#  related or neighboring rights to this work.  This work is published from:
+#  United States.
+#
+# Build libpng with support for pngcp.  This means just png_read_png,
+# png_write_png and small number of configuration settings.
+#
+everything = off
+
+# This option is specific to this configuration; it adds a #define to the
+# generated pnglibconf.h which turns on the (not portable) timing option for
+# pngcp.  Note that any option is automatically preceded by PNG_; there is no
+# way round this and this is deliberate.
+option PNGCP_TIMING
+
+# Because of the everything off above the option must also be turned on.  This
+# may not be done in one step because it is safer and avoids mis-spelled options
+# in user .dfa files to error out if an unrecognized option is turned on.
+option PNGCP_TIMING on
+
+# Options to turn on png_read_png and png_write_png:
+option INFO_IMAGE on
+option SEQUENTIAL_READ on
+option EASY_ACCESS on
+option WRITE on
+option WRITE_16BIT on
+option WRITE_FILTER on
+
+# pngcp needs this to preserve unknown chunks, switching all these on means that
+# pngcp can work without explicit known chunk reading suppport
+option UNKNOWN_CHUNKS on
+option SET_UNKNOWN_CHUNKS on
+option HANDLE_AS_UNKNOWN on
+option SAVE_UNKNOWN_CHUNKS on
+option WRITE_UNKNOWN_CHUNKS on
+
+# pngcp needs this to handle palette files with invalid indices:
+option CHECK_FOR_INVALID_INDEX on
+option GET_PALETTE_MAX on
+
+# Pre-libpng 1.7 pngcp has to stash text chunks manually, post 1.7 without this
+# text chunks should be handled as unknown ok.
+option TEXT on
+
+# this is used to turn off limits:
+option USER_LIMITS on
+option SET_USER_LIMITS on
+
+# these are are just required for specific customizations
+option WRITE_CUSTOMIZE_ZTXT_COMPRESSION on
+option WRITE_CUSTOMIZE_COMPRESSION on
diff --git a/contrib/intel/filter_sse2_intrinsics.c b/contrib/intel/filter_sse2_intrinsics.c
index aea3f86..b02840c 100644
--- a/contrib/intel/filter_sse2_intrinsics.c
+++ b/contrib/intel/filter_sse2_intrinsics.c
@@ -6,7 +6,7 @@
  * Derived from arm/filter_neon_intrinsics.c, which was
  * Copyright (c) 2014,2016 Glenn Randers-Pehrson
  *
- * Last changed in libpng 1.6.22 [May 26, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -208,7 +208,7 @@
    x = _mm_xor_si128(x, is_negative);
 
    /* +1 to negative lanes, else +0. */
-   x = _mm_add_epi16(x, _mm_srli_epi16(is_negative, 15));
+   x = _mm_sub_epi16(x, is_negative);
    return x;
 #endif
 }
diff --git a/contrib/intel/intel_sse.patch b/contrib/intel/intel_sse.patch
index f000c11..c5579e3 100644
--- a/contrib/intel/intel_sse.patch
+++ b/contrib/intel/intel_sse.patch
@@ -55,7 +55,7 @@
 diff --git a/Makefile.am b/Makefile.am
 --- a/Makefile.am	2016-05-17 18:15:12.000000000 -0400
 +++ b/Makefile.am	2016-05-25 19:48:10.631751170 -0400
-@@ -89,16 +89,20 @@ libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@_la_SO
+@@ -92,16 +92,20 @@ libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@_la_SO
  	pngset.c pngtrans.c pngwio.c pngwrite.c pngwtran.c pngwutil.c\
  	png.h pngconf.h pngdebug.h pnginfo.h pngpriv.h pngstruct.h pngusr.dfa
  
@@ -77,8 +77,8 @@
  #   Versioned symbols and restricted exports
  if HAVE_SOLARIS_LD
 diff --git a/pngpriv.h b/pngpriv.h
---- a/pngpriv.h	2016-05-31 09:20:34.442885047 -0500
-+++ b/pngpriv.h	2016-05-31 09:14:54.583492341 -0500
+--- a/pngpriv.h	2016-08-01 18:13:38.770128810 -0500
++++ b/pngpriv.h	2016-08-01 18:50:19.130179017 -0500
 @@ -177,16 +177,52 @@
  #  endif /* !PNG_ARM_NEON_IMPLEMENTATION */
  
@@ -132,7 +132,7 @@
   * PNG_BUILD_DLL must not be set.  To avoid the code below kicking in build a
   * static library of libpng then link the DLL against that.
   */
-@@ -1184,16 +1220,29 @@ PNG_INTERNAL_FUNCTION(void,png_read_filt
+@@ -1185,16 +1221,31 @@ PNG_INTERNAL_FUNCTION(void,png_read_filt
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_avg4_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
@@ -140,7 +140,9 @@
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_paeth4_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
- 
+ #endif
++ 
++#if PNG_INTEL_SSE_IMPLEMENTATION > 0
 +PNG_INTERNAL_FUNCTION(void,png_read_filter_row_sub3_sse2,(png_row_infop
 +    row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
 +PNG_INTERNAL_FUNCTION(void,png_read_filter_row_sub4_sse2,(png_row_infop
@@ -153,7 +155,8 @@
 +    row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
 +PNG_INTERNAL_FUNCTION(void,png_read_filter_row_paeth4_sse2,(png_row_infop
 +    row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
-+
++#endif
+ 
  /* Choose the best filter to use and filter the row data */
  PNG_INTERNAL_FUNCTION(void,png_write_find_filter,(png_structrp png_ptr,
      png_row_infop row_info),PNG_EMPTY);
@@ -161,18 +164,19 @@
  #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_read_IDAT_data,(png_structrp png_ptr,
     png_bytep output, png_alloc_size_t avail_out),PNG_EMPTY);
-    /* Read 'avail_out' bytes of data from the IDAT stream.  If the output buffer
-@@ -1910,16 +1959,18 @@ PNG_INTERNAL_FUNCTION(void, PNG_FILTER_O
-    /* Just declare the optimization that will be used */
- #else
+@@ -1914,16 +1965,20 @@ PNG_INTERNAL_FUNCTION(void, PNG_FILTER_O
     /* List *all* the possible optimizations here - this branch is required if
      * the builder of libpng passes the definition of PNG_FILTER_OPTIMIZATIONS in
      * CFLAGS in place of CPPFLAGS *and* uses symbol prefixing.
      */
+ #  if PNG_ARM_NEON_OPT > 0
  PNG_INTERNAL_FUNCTION(void, png_init_filter_functions_neon,
     (png_structp png_ptr, unsigned int bpp), PNG_EMPTY);
+ #  endif
++#  if PNG_INTEL_SSE_IMPLEMENTATION > 0
 +PNG_INTERNAL_FUNCTION(void, png_init_filter_functions_sse2,
 +   (png_structp png_ptr, unsigned int bpp), PNG_EMPTY);
++#  endif
  #endif
  
  PNG_INTERNAL_FUNCTION(png_uint_32, png_check_keyword, (png_structrp png_ptr,
diff --git a/contrib/libtests/pngimage.c b/contrib/libtests/pngimage.c
index 2ebe553..9ae402c 100644
--- a/contrib/libtests/pngimage.c
+++ b/contrib/libtests/pngimage.c
@@ -2,7 +2,7 @@
  *
  * Copyright (c) 2015,2016 John Cunningham Bowler
  *
- * Last changed in libpng 1.6.22 [May 26, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -45,8 +45,19 @@
 #  define SKIP 0
 #endif
 
-#if defined(PNG_INFO_IMAGE_SUPPORTED) && defined(PNG_SEQUENTIAL_READ_SUPPORTED)\
-    && (defined(PNG_READ_PNG_SUPPORTED) || PNG_LIBPNG_VER < 10700)
+#if PNG_LIBPNG_VER < 10700
+   /* READ_PNG and WRITE_PNG were not defined, so: */
+#  ifdef PNG_INFO_IMAGE_SUPPORTED
+#     ifdef PNG_SEQUENTIAL_READ_SUPPORTED
+#        define PNG_READ_PNG_SUPPORTED
+#     endif /* SEQUENTIAL_READ */
+#     ifdef PNG_WRITE_SUPPORTED
+#        define PNG_WRITE_PNG_SUPPORTED
+#     endif /* WRITE */
+#  endif /* INFO_IMAGE */
+#endif /* pre 1.7.0 */
+
+#ifdef PNG_READ_PNG_SUPPORTED
 /* If a transform is valid on both read and write this implies that if the
  * transform is applied to read it must also be applied on write to produce
  * meaningful data.  This is because these transforms when performed on read
@@ -395,7 +406,7 @@
    buffer_destroy_list(list);
 }
 
-#ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_PNG_SUPPORTED
 static void
 buffer_start_write(struct buffer *buffer)
 {
@@ -565,7 +576,7 @@
    png_structp    read_pp;
    png_infop      read_ip;
 
-#  ifdef PNG_WRITE_SUPPORTED
+#  ifdef PNG_WRITE_PNG_SUPPORTED
       /* Used to write a new image (the original info_ptr is used) */
       png_structp   write_pp;
       struct buffer written_file;   /* where the file gets written */
@@ -592,7 +603,7 @@
    dp->read_ip = NULL;
    buffer_init(&dp->original_file);
 
-#  ifdef PNG_WRITE_SUPPORTED
+#  ifdef PNG_WRITE_PNG_SUPPORTED
       dp->write_pp = NULL;
       buffer_init(&dp->written_file);
 #  endif
@@ -605,7 +616,7 @@
       png_destroy_read_struct(&dp->read_pp, &dp->read_ip, NULL);
 }
 
-#ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_PNG_SUPPORTED
 static void
 display_clean_write(struct display *dp)
 {
@@ -617,7 +628,7 @@
 static void
 display_clean(struct display *dp)
 {
-#  ifdef PNG_WRITE_SUPPORTED
+#  ifdef PNG_WRITE_PNG_SUPPORTED
       display_clean_write(dp);
 #  endif
    display_clean_read(dp);
@@ -635,7 +646,7 @@
 display_destroy(struct display *dp)
 {
     /* Release any memory held in the display. */
-#  ifdef PNG_WRITE_SUPPORTED
+#  ifdef PNG_WRITE_PNG_SUPPORTED
       buffer_destroy(&dp->written_file);
 #  endif
 
@@ -1082,6 +1093,7 @@
       }
 
       else
+#     ifdef PNG_sBIT_SUPPORTED
       {
          unsigned long y;
          int bpp;   /* bits-per-pixel then bytes-per-pixel */
@@ -1243,12 +1255,16 @@
             }
          } /* for y */
       }
+#     else /* !sBIT */
+         display_log(dp, INTERNAL_ERROR,
+               "active shift transform but no sBIT support");
+#     endif /* !sBIT */
    }
 
    return 1; /* compare succeeded */
 }
 
-#ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_PNG_SUPPORTED
 static void
 buffer_write(struct display *dp, struct buffer *buffer, png_bytep data,
    png_size_t size)
@@ -1347,7 +1363,7 @@
     */
    display_clean_write(dp);
 }
-#endif /* WRITE_SUPPORTED */
+#endif /* WRITE_PNG */
 
 static int
 skip_transform(struct display *dp, int tr)
@@ -1409,7 +1425,7 @@
          return; /* no point testing more */
    }
 
-#ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_PNG_SUPPORTED
    /* Second test: write the original PNG data out to a new file (to test the
     * write side) then read the result back in and make sure that it hasn't
     * changed.
@@ -1450,7 +1466,7 @@
           * out and read it back in again (without the reversible transforms)
           * we should get back to the place where we started.
           */
-#ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_PNG_SUPPORTED
          if ((current & write_transforms) == current)
          {
             /* All transforms reversible: write the PNG with the transformations
@@ -1686,7 +1702,7 @@
       return errors != 0;
    }
 }
-#else /* !INFO_IMAGE || !SEQUENTIAL_READ || !READ_PNG*/
+#else /* !READ_PNG */
 int
 main(void)
 {
diff --git a/contrib/libtests/pngstest.c b/contrib/libtests/pngstest.c
index dffd7c1..30f57a9 100644
--- a/contrib/libtests/pngstest.c
+++ b/contrib/libtests/pngstest.c
@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2013-2016 John Cunningham Bowler
  *
- * Last changed in libpng 1.6.22 [May 26, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -26,15 +26,6 @@
 #  include <config.h>
 #endif
 
-/* 1.6.1 added support for the configure test harness, which uses 77 to indicate
- * a skipped test, in earlier versions we need to succeed on a skipped test, so:
- */
-#if PNG_LIBPNG_VER >= 10601 && defined(HAVE_CONFIG_H)
-#  define SKIP 77
-#else
-#  define SKIP 0
-#endif
-
 /* Define the following to use this test against your installed libpng, rather
  * than the one being built here:
  */
@@ -44,6 +35,15 @@
 #  include "../../png.h"
 #endif
 
+/* 1.6.1 added support for the configure test harness, which uses 77 to indicate
+ * a skipped test, in earlier versions we need to succeed on a skipped test, so:
+ */
+#if PNG_LIBPNG_VER >= 10601 && defined(HAVE_CONFIG_H)
+#  define SKIP 77
+#else
+#  define SKIP 0
+#endif
+
 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED /* Else nothing can be done */
 #include "../tools/sRGB.h"
 
diff --git a/contrib/libtests/pngvalid.c b/contrib/libtests/pngvalid.c
index 7a42d13..9d3beb5 100644
--- a/contrib/libtests/pngvalid.c
+++ b/contrib/libtests/pngvalid.c
@@ -1,7 +1,7 @@
 
 /* pngvalid.c - validate libpng by constructing then reading png files.
  *
- * Last changed in libpng 1.6.23 [June 9, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 2014-2016 Glenn Randers-Pehrson
  * Written by John Cunningham Bowler
  *
@@ -1115,7 +1115,7 @@
    if (!ps->expect_warning)
       store_log(ps, pp, message, 0 /* warning */);
    else
-     ps->saw_warning = 1;
+      ps->saw_warning = 1;
 }
 
 /* These somewhat odd functions are used when reading an image to ensure that
@@ -1589,7 +1589,7 @@
          {
             if (chunkpos < chunklen-4U)
             {
-               uInt avail = -1;
+               uInt avail = (uInt)-1;
 
                if (avail > (IDAT_len-4U) - IDAT_pos)
                   avail = (uInt)/*SAFE*/((IDAT_len-4U) - IDAT_pos);
diff --git a/contrib/tools/chkfmt b/contrib/tools/chkfmt
index 9da6475..a1b88cc 100755
--- a/contrib/tools/chkfmt
+++ b/contrib/tools/chkfmt
@@ -1,4 +1,11 @@
 #!/bin/sh
+
+# chkfmt
+#
+# COPYRIGHT: Written by John Cunningham Bowler, 2010.
+# To the extent possible under law, the author has waived all copyright and
+# related or neighboring rights to this work.  This work is published from:
+# United States.
 #
 # Check the format of the source files in the current directory - checks for a
 # line length of 80 characters max and no tab characters.
diff --git a/contrib/tools/pngcp.c b/contrib/tools/pngcp.c
new file mode 100644
index 0000000..e82dddc
--- /dev/null
+++ b/contrib/tools/pngcp.c
@@ -0,0 +1,2453 @@
+/* pngcp.c
+ *
+ * Copyright (c) 2016 John Cunningham Bowler
+ *
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ *
+ * This is an example of copying a PNG without changes using the png_read_png
+ * and png_write_png interfaces.  A considerable number of options are provided
+ * to manipulate the compression of the PNG data and other compressed chunks.
+ *
+ * For a more extensive example that uses the transforms see
+ * contrib/libtests/pngimage.c in the libpng distribution.
+ */
+#include "pnglibconf.h" /* To find how libpng was configured. */
+
+#ifdef PNG_PNGCP_TIMING_SUPPORTED
+   /* WARNING:
+    *
+    * This test is here to allow POSIX.1b extensions to be used if enabled in
+    * the compile; specifically the code requires_POSIX_C_SOURCE support of
+    * 199309L or later to enable clock_gettime use.
+    *
+    * IF this causes problems THEN compile with a strict ANSI C compiler and let
+    * this code turn on the POSIX features that it minimally requires.
+    *
+    * IF this does not work there is probably a bug in your ANSI C compiler or
+    * your POSIX implementation.
+    */
+#  define _POSIX_C_SOURCE 199309L
+#else /* No timing support required */
+#  define _POSIX_SOURCE 1
+#endif
+
+#if defined(HAVE_CONFIG_H) && !defined(PNG_NO_CONFIG_H)
+#  include <config.h>
+#endif
+
+#include <stdio.h>
+
+/* Define the following to use this test against your installed libpng, rather
+ * than the one being built here:
+ */
+#ifdef PNG_FREESTANDING_TESTS
+#  include <png.h>
+#else
+#  include "../../png.h"
+#endif
+
+#if PNG_LIBPNG_VER < 10700
+   /* READ_PNG and WRITE_PNG were not defined, so: */
+#  ifdef PNG_INFO_IMAGE_SUPPORTED
+#     ifdef PNG_SEQUENTIAL_READ_SUPPORTED
+#        define PNG_READ_PNG_SUPPORTED
+#     endif /* SEQUENTIAL_READ */
+#     ifdef PNG_WRITE_SUPPORTED
+#        define PNG_WRITE_PNG_SUPPORTED
+#     endif /* WRITE */
+#  endif /* INFO_IMAGE */
+#endif /* pre 1.7.0 */
+
+#if (defined(PNG_READ_PNG_SUPPORTED)) && (defined(PNG_WRITE_PNG_SUPPORTED))
+#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <limits.h>
+#include <assert.h>
+
+#include <unistd.h>
+#include <sys/stat.h>
+
+#include <zlib.h>
+
+#ifndef PNG_SETJMP_SUPPORTED
+#  include <setjmp.h> /* because png.h did *not* include this */
+#endif
+
+#ifdef __cplusplus
+#  define voidcast(type, value) static_cast<type>(value)
+#else
+#  define voidcast(type, value) (value)
+#endif /* __cplusplus */
+
+#ifdef __GNUC__
+   /* Many versions of GCC erroneously report that local variables unmodified
+    * within the scope of a setjmp may be clobbered.  This hacks round the
+    * problem (sometimes) without harming other compilers.
+    */
+#  define gv volatile
+#else
+#  define gv
+#endif
+
+/* 'CLOCK_PROCESS_CPUTIME_ID' is one of the clock timers for clock_gettime.  It
+ * need not be supported even when clock_gettime is available.  It returns the
+ * 'CPU' time the process has consumed.  'CPU' time is assumed to include time
+ * when the CPU is actually blocked by a pending cache fill but not time
+ * waiting for page faults.  The attempt is to get a measure of the actual time
+ * the implementation takes to read a PNG ignoring the potentially very large IO
+ * overhead.
+ */
+#ifdef PNG_PNGCP_TIMING_SUPPORTED
+#  include <time.h>   /* clock_gettime and associated definitions */
+#  ifndef CLOCK_PROCESS_CPUTIME_ID
+      /* Prevent inclusion of the spurious code: */
+#     undef PNG_PNGCP_TIMING_SUPPORTED
+#  endif
+#endif /* PNGCP_TIMING */
+
+/* So if the timing feature has been activated: */
+
+/* This structure is used to control the test of a single file. */
+typedef enum
+{
+   VERBOSE,        /* switches on all messages */
+   INFORMATION,
+   WARNINGS,       /* switches on warnings */
+   LIBPNG_WARNING,
+   APP_WARNING,
+   ERRORS,         /* just errors */
+   APP_FAIL,       /* continuable error - no need to longjmp */
+   LIBPNG_ERROR,   /* this and higher cause a longjmp */
+   LIBPNG_BUG,     /* erroneous behavior in libpng */
+   APP_ERROR,      /* such as out-of-memory in a callback */
+   QUIET,          /* no normal messages */
+   USER_ERROR,     /* such as file-not-found */
+   INTERNAL_ERROR
+} error_level;
+#define LEVEL_MASK      0xf   /* where the level is in 'options' */
+
+#define STRICT          0x010 /* Fail on warnings as well as errors */
+#define LOG             0x020 /* Log pass/fail to stdout */
+#define CONTINUE        0x040 /* Continue on APP_FAIL errors */
+#define SIZES           0x080 /* Report input and output sizes */
+#define SEARCH          0x100 /* Search IDAT compression options */
+#define NOWRITE         0x200 /* Do not write an output file */
+#ifdef PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED
+#  define IGNORE_INDEX  0x400 /* Ignore out of range palette indices (BAD!) */
+#  ifdef PNG_GET_PALETTE_MAX_SUPPORTED
+#     define FIX_INDEX  0x800 /* 'Fix' out of range palette indices (OK) */
+#  endif /* GET_PALETTE_MAX */
+#endif /* CHECK_FOR_INVALID_INDEX */
+#define OPTION     0x80000000 /* Used for handling options */
+#define LIST       0x80000001 /* Used for handling options */
+
+/* Result masks apply to the result bits in the 'results' field below; these
+ * bits are simple 1U<<error_level.  A pass requires either nothing worse than
+ * warnings (--relaxes) or nothing worse than information (--strict)
+ */
+#define RESULT_STRICT(r)   (((r) & ~((1U<<WARNINGS)-1)) == 0)
+#define RESULT_RELAXED(r)  (((r) & ~((1U<<ERRORS)-1)) == 0)
+
+/* OPTION DEFINITIONS */
+static const char range_lo[] = "low";
+static const char range_hi[] = "high";
+static const char all[] = "all";
+#define RANGE(lo,hi) { range_lo, lo }, { range_hi, hi }
+typedef struct value_list
+{
+   const char *name;  /* the command line name of the value */
+   int         value; /* the actual value to use */
+}  value_list;
+
+static const value_list
+#ifdef PNG_SW_COMPRESS_png_level
+vl_compression[] =
+{
+   /* Overall compression control.  The order controls the search order for
+    * 'all'.  Since the search is for the smallest the order used is low memory
+    * then high speed.
+    */
+   { "low-memory",      PNG_COMPRESSION_LOW_MEMORY },
+   { "high-speed",      PNG_COMPRESSION_HIGH_SPEED },
+   { "high-read-speed", PNG_COMPRESSION_HIGH_READ_SPEED },
+   { "low",             PNG_COMPRESSION_LOW },
+   { "medium",          PNG_COMPRESSION_MEDIUM },
+   { "old",             PNG_COMPRESSION_COMPAT },
+   { "high",            PNG_COMPRESSION_HIGH },
+   { all, 0 }
+},
+#endif /* SW_COMPRESS_png_level */
+
+#if defined(PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED) ||\
+    defined(PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED)
+vl_strategy[] =
+{
+   /* This controls the order of search. */
+   { "huffman", Z_HUFFMAN_ONLY },
+   { "RLE", Z_RLE },
+   { "fixed", Z_FIXED }, /* the remainder do window searchs */
+   { "filtered", Z_FILTERED },
+   { "default", Z_DEFAULT_STRATEGY },
+   { all, 0 }
+},
+#ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
+vl_windowBits_text[] =
+{
+   { "default", MAX_WBITS/*from zlib*/ },
+   { "minimum", 8 },
+   RANGE(8, MAX_WBITS/*from zlib*/),
+   { all, 0 }
+},
+#endif /* text compression */
+vl_level[] =
+{
+   { "default", Z_DEFAULT_COMPRESSION /* this is -1 */ },
+   { "none", Z_NO_COMPRESSION },
+   { "speed", Z_BEST_SPEED },
+   { "best", Z_BEST_COMPRESSION },
+   { "0", Z_NO_COMPRESSION },
+   RANGE(1, 9), /* this deliberately excludes '0' */
+   { all, 0 }
+},
+vl_memLevel[] =
+{
+   { "max", MAX_MEM_LEVEL }, /* zlib maximum */
+   { "1", 1 }, /* zlib minimum */
+   { "default", 8 }, /* zlib default */
+   { "2", 2 },
+   { "3", 3 },
+   { "4", 4 },
+   { "5", 5 }, /* for explicit testing */
+   RANGE(6, MAX_MEM_LEVEL/*zlib*/), /* exclude 5 and below: zlib bugs */
+   { all, 0 }
+},
+#endif /* WRITE_CUSTOMIZE_*COMPRESSION */
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+vl_filter[] =
+{
+   { all,      PNG_ALL_FILTERS   },
+   { "off",    PNG_NO_FILTERS    },
+   { "none",   PNG_FILTER_NONE   },
+   { "sub",    PNG_FILTER_SUB    },
+   { "up",     PNG_FILTER_UP     },
+   { "avg",    PNG_FILTER_AVG    },
+   { "paeth",  PNG_FILTER_PAETH  }
+},
+#endif /* WRITE_FILTER */
+#ifdef PNG_PNGCP_TIMING_SUPPORTED
+#  define PNGCP_TIME_READ  1
+#  define PNGCP_TIME_WRITE 2
+vl_time[] =
+{
+   { "both",  PNGCP_TIME_READ+PNGCP_TIME_WRITE },
+   { "off",   0 },
+   { "read",  PNGCP_TIME_READ },
+   { "write", PNGCP_TIME_WRITE }
+},
+#endif /* PNGCP_TIMING */
+vl_IDAT_size[] = /* for png_set_IDAT_size */
+{
+   { "default", 0x7FFFFFFF },
+   { "minimal", 1 },
+   RANGE(1, 0x7FFFFFFF)
+},
+#ifndef PNG_SW_IDAT_size
+   /* Pre 1.7 API: */
+#  define png_set_IDAT_size(p,v) png_set_compression_buffer_size(p, v)
+#endif /* !SW_IDAT_size */
+#define SL 8 /* stack limit in display, below */
+vl_log_depth[] = { { "on", 1 }, { "off", 0 }, RANGE(0, SL) },
+vl_on_off[] = { { "on", 1 }, { "off", 0 } };
+
+#ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
+static value_list
+vl_windowBits_IDAT[] =
+{
+   { "default", MAX_WBITS },
+   { "small", 9 },
+   RANGE(8, MAX_WBITS), /* modified by set_windowBits_hi */
+   { all, 0 }
+};
+#endif /* IDAT compression */
+
+typedef struct option
+{
+   const char       *name;         /* name of the option */
+   png_uint_32       opt;          /* an option, or OPTION or LIST */
+   png_byte          search;       /* Search on --search */
+   png_byte          value_count;  /* length of the list of values: */
+   const value_list *values;       /* values for OPTION or LIST */
+}  option;
+
+static const option options[] =
+{
+   /* struct display options, these are set when the command line is read */
+#  define S(n,v) { #n, v, 0, 2, vl_on_off },
+   S(verbose,  VERBOSE)
+   S(warnings, WARNINGS)
+   S(errors,   ERRORS)
+   S(quiet,    QUIET)
+   S(strict,   STRICT)
+   S(log,      LOG)
+   S(continue, CONTINUE)
+   S(sizes,    SIZES)
+   S(search,   SEARCH)
+   S(nowrite,  NOWRITE)
+#  ifdef IGNORE_INDEX
+      S(ignore-palette-index, IGNORE_INDEX)
+#  endif /* IGNORE_INDEX */
+#  ifdef FIX_INDEX
+      S(fix-palette-index, FIX_INDEX)
+#  endif /* FIX_INDEX */
+#  undef S
+
+   /* OPTION settings, these and LIST settings are read on demand */
+#  define VLNAME(name) vl_ ## name
+#  define VLSIZE(name) voidcast(png_byte,\
+                           (sizeof VLNAME(name))/(sizeof VLNAME(name)[0]))
+#  define VL(oname, name, type, search)\
+   { oname, type, search, VLSIZE(name), VLNAME(name) },
+#  define VLO(oname, name, search) VL(oname, name, OPTION, search)
+
+#  ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
+#     define VLCIDAT(name) VLO(#name, name, 1/*search*/)
+#     ifdef PNG_SW_COMPRESS_level
+#        define VLCiCCP(name) VLO("ICC-profile-" #name, name, 0/*search*/)
+#     else
+#        define VLCiCCP(name)
+#     endif
+#  else
+#     define VLCIDAT(name)
+#     define VLCiCCP(name)
+#  endif /* WRITE_CUSTOMIZE_COMPRESSION */
+
+#  ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
+#     define VLCzTXt(name) VLO("text-" #name, name, 0/*search*/)
+#  else
+#     define VLCzTXt(name)
+#  endif /* WRITE_CUSTOMIZE_ZTXT_COMPRESSION */
+
+#  define VLC(name) VLCIDAT(name) VLCiCCP(name) VLCzTXt(name)
+
+#  ifdef PNG_SW_COMPRESS_png_level
+      /* The libpng compression level isn't searched beause it justs sets the
+       * other things that are searched!
+       */
+      VLO("compression", compression, 0)
+      VLO("text-compression", compression, 0)
+      VLO("ICC-profile-compression", compression, 0)
+#  endif /* SW_COMPRESS_png_level */
+   VLC(strategy)
+   VLO("windowBits", windowBits_IDAT, 1)
+#  ifdef PNG_SW_COMPRESS_windowBits
+      VLO("ICC-profile-windowBits", windowBits_text/*sic*/, 0)
+#  endif
+   VLO("text-windowBits", windowBits_text, 0)
+   VLC(level)
+   VLC(memLevel)
+   VLO("IDAT-size", IDAT_size, 0)
+   VLO("log-depth", log_depth, 0)
+
+#  undef VLO
+
+   /* LIST settings */
+#  define VLL(name, search) VL(#name, name, LIST, search)
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+   VLL(filter, 0)
+#endif /* WRITE_FILTER */
+#ifdef PNG_PNGCP_TIMING_SUPPORTED
+   VLL(time, 0)
+#endif /* PNGCP_TIMING */
+#  undef VLL
+#  undef VL
+};
+
+#ifdef __cplusplus
+   static const size_t option_count((sizeof options)/(sizeof options[0]));
+#else /* !__cplusplus */
+#  define option_count ((sizeof options)/(sizeof options[0]))
+#endif /* !__cplusplus */
+
+static const char *
+cts(int ct)
+{
+   switch (ct)
+   {
+      case PNG_COLOR_TYPE_PALETTE:     return "P";
+      case PNG_COLOR_TYPE_GRAY:        return "G";
+      case PNG_COLOR_TYPE_GRAY_ALPHA:  return "GA";
+      case PNG_COLOR_TYPE_RGB:         return "RGB";
+      case PNG_COLOR_TYPE_RGB_ALPHA:   return "RGBA";
+      default:                         return "INVALID";
+   }
+}
+
+struct display
+{
+   jmp_buf          error_return;      /* Where to go to on error */
+   unsigned int     errset;            /* error_return is set */
+
+   const char      *operation;         /* What is happening */
+   const char      *filename;          /* The name of the original file */
+   const char      *output_file;       /* The name of the output file */
+
+   /* Used on both read and write: */
+   FILE            *fp;
+
+   /* Used on a read, both the original read and when validating a written
+    * image.
+    */
+   png_alloc_size_t read_size;
+   png_structp      read_pp;
+   png_infop        ip;
+#  if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+      png_textp     text_ptr; /* stash of text chunks */
+      int           num_text;
+      int           text_stashed;
+#  endif /* pre 1.7 */
+
+#  ifdef PNG_PNGCP_TIMING_SUPPORTED
+      struct timespec   read_time;
+      struct timespec   read_time_total;
+      struct timespec   write_time;
+      struct timespec   write_time_total;
+#  endif /* PNGCP_TIMING */
+
+   /* Used to write a new image (the original info_ptr is used) */
+#  define MAX_SIZE ((png_alloc_size_t)(-1))
+   png_alloc_size_t write_size;
+   png_alloc_size_t best_size;
+   png_structp      write_pp;
+
+   /* Base file information */
+   png_alloc_size_t size;
+   png_uint_32      w;
+   png_uint_32      h;
+   int              bpp;
+   png_byte         ct;
+   int              no_warnings;       /* Do not output libpng warnings */
+   int              min_windowBits;    /* The windowBits range is 8..8 */
+
+   /* Options handling */
+   png_uint_32      results;             /* A mask of errors seen */
+   png_uint_32      options;             /* See display_log below */
+   png_byte         entry[option_count]; /* The selected entry+1 of an option
+                                          * that appears on the command line, or
+                                          * 0 if it was not given. */
+   int              value[option_count]; /* Corresponding value */
+
+   /* Compression exhaustive testing */
+   /* Temporary variables used only while testing a single collection of
+    * settings:
+    */
+   unsigned int     csp;               /* next stack entry to use */
+   unsigned int     nsp;               /* highest active entry+1 found so far */
+
+   /* Values used while iterating through all the combinations of settings for a
+    * single file:
+    */
+   unsigned int     tsp;               /* nsp from the last run; this is the
+                                        * index+1 of the highest active entry on
+                                        * this run; this entry will be advanced.
+                                        */
+   int              opt_string_start;  /* Position in buffer for the first
+                                        * searched option; non-zero if earlier
+                                        * options were set on the command line.
+                                        */
+   struct stack
+   {
+      png_alloc_size_t best_size;      /* Best so far for this option */
+      png_alloc_size_t lo_size;
+      png_alloc_size_t hi_size;
+      int              lo, hi;         /* For binary chop of a range */
+      int              best_val;       /* Best value found so far */
+      int              opt_string_end; /* End of the option string in 'curr' */
+      png_byte         opt;            /* The option being tested */
+      png_byte         entry;          /* The next value entry to be tested */
+      png_byte         end;            /* This is the last entry */
+   }                stack[SL];         /* Stack of entries being tested */
+   char             curr[32*SL];       /* current options being tested */
+   char             best[32*SL];       /* best options */
+
+   char             namebuf[FILENAME_MAX]; /* output file name */
+};
+
+static void
+display_init(struct display *dp)
+   /* Call this only once right at the start to initialize the control
+    * structure, the (struct buffer) lists are maintained across calls - the
+    * memory is not freed.
+    */
+{
+   memset(dp, 0, sizeof *dp);
+   dp->operation = "internal error";
+   dp->filename = "command line";
+   dp->output_file = "no output file";
+   dp->options = WARNINGS; /* default to !verbose, !quiet */
+   dp->fp = NULL;
+   dp->read_pp = NULL;
+   dp->ip = NULL;
+   dp->write_pp = NULL;
+   dp->min_windowBits = -1; /* this is an OPTIND, so -1 won't match anything */
+#  if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+      dp->text_ptr = NULL;
+      dp->num_text = 0;
+      dp->text_stashed = 0;
+#  endif /* pre 1.7 */
+}
+
+static void
+display_clean_read(struct display *dp)
+{
+   if (dp->read_pp != NULL)
+      png_destroy_read_struct(&dp->read_pp, NULL, NULL);
+
+   if (dp->fp != NULL)
+   {
+      FILE *fp = dp->fp;
+      dp->fp = NULL;
+      (void)fclose(fp);
+   }
+}
+
+static void
+display_clean_write(struct display *dp)
+{
+   if (dp->fp != NULL)
+   {
+      FILE *fp = dp->fp;
+      dp->fp = NULL;
+      (void)fclose(fp);
+   }
+
+   if (dp->write_pp != NULL)
+      png_destroy_write_struct(&dp->write_pp, dp->tsp > 0 ? NULL : &dp->ip);
+}
+
+static void
+display_clean(struct display *dp)
+{
+   display_clean_read(dp);
+   display_clean_write(dp);
+   dp->output_file = NULL;
+
+#  if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+      /* This is actually created and used by the write code, but only
+       * once; it has to be retained for subsequent writes of the same file.
+       */
+      if (dp->text_stashed)
+      {
+         dp->text_stashed = 0;
+         dp->num_text = 0;
+         free(dp->text_ptr);
+         dp->text_ptr = NULL;
+      }
+#  endif /* pre 1.7 */
+
+   /* leave the filename for error detection */
+   dp->results = 0; /* reset for next time */
+}
+
+static void
+display_destroy(struct display *dp)
+{
+   /* Release any memory held in the display. */
+   display_clean(dp);
+}
+
+static struct display *
+get_dp(png_structp pp)
+   /* The display pointer is always stored in the png_struct error pointer */
+{
+   struct display *dp = (struct display*)png_get_error_ptr(pp);
+
+   if (dp == NULL)
+   {
+      fprintf(stderr, "pngcp: internal error (no display)\n");
+      exit(99); /* prevents a crash */
+   }
+
+   return dp;
+}
+
+/* error handling */
+#ifdef __GNUC__
+#  define VGATTR __attribute__((__format__ (__printf__,3,4)))
+   /* Required to quiet GNUC warnings when the compiler sees a stdarg function
+    * that calls one of the stdio v APIs.
+    */
+#else
+#  define VGATTR
+#endif
+static void VGATTR
+display_log(struct display *dp, error_level level, const char *fmt, ...)
+   /* 'level' is as above, fmt is a stdio style format string.  This routine
+    * does not return if level is above LIBPNG_WARNING
+    */
+{
+   dp->results |= 1U << level;
+
+   if (level > (error_level)(dp->options & LEVEL_MASK))
+   {
+      const char *lp;
+      va_list ap;
+
+      switch (level)
+      {
+         case INFORMATION:    lp = "information"; break;
+         case LIBPNG_WARNING: lp = "warning(libpng)"; break;
+         case APP_WARNING:    lp = "warning(pngcp)"; break;
+         case APP_FAIL:       lp = "error(continuable)"; break;
+         case LIBPNG_ERROR:   lp = "error(libpng)"; break;
+         case LIBPNG_BUG:     lp = "bug(libpng)"; break;
+         case APP_ERROR:      lp = "error(pngcp)"; break;
+         case USER_ERROR:     lp = "error(user)"; break;
+
+         case INTERNAL_ERROR: /* anything unexpected is an internal error: */
+         case VERBOSE: case WARNINGS: case ERRORS: case QUIET:
+         default:             lp = "bug(pngcp)"; break;
+      }
+
+      fprintf(stderr, "%s: %s: %s",
+         dp->filename != NULL ? dp->filename : "<stdin>", lp, dp->operation);
+
+      fprintf(stderr, ": ");
+
+      va_start(ap, fmt);
+      vfprintf(stderr, fmt, ap);
+      va_end(ap);
+
+      fputc('\n', stderr);
+   }
+   /* else do not output any message */
+
+   /* Errors cause this routine to exit to the fail code */
+   if (level > APP_FAIL || (level > ERRORS && !(dp->options & CONTINUE)))
+   {
+      if (dp->errset)
+         longjmp(dp->error_return, level);
+
+      else
+         exit(99);
+   }
+}
+
+#if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+static void
+text_stash(struct display *dp)
+{
+   /* libpng 1.6 and earlier fixed a bug whereby text chunks were written
+    * multiple times by png_write_png; the issue was that png_write_png passed
+    * the same png_info to both png_write_info and png_write_end.  Rather than
+    * fixing it by recording the information in the png_struct, or by recording
+    * where to write the chunks, the fix made was to change the 'compression'
+    * field of the chunk to invalid values, rendering the png_info somewhat
+    * useless.
+    *
+    * The only fix for this given that we use the png_info more than once is to
+    * make a copy of the text chunks and png_set_text it each time.  This adds a
+    * text chunks, so they get replicated, but only the new set gets written
+    * each time.  This uses memory like crazy but there is no way to delete the
+    * useless chunks from the png_info.
+    *
+    * To make this slightly more efficient only the top level structure is
+    * copied; since the old strings are actually preserved (in 1.6 and earlier)
+    * this happens to work.
+    */
+   png_textp chunks = NULL;
+
+   dp->num_text = png_get_text(dp->write_pp, dp->ip, &chunks, NULL);
+
+   if (dp->num_text > 0)
+   {
+      dp->text_ptr = voidcast(png_textp, malloc(dp->num_text * sizeof *chunks));
+
+      if (dp->text_ptr == NULL)
+         display_log(dp, APP_ERROR, "text chunks: stash malloc failed");
+
+      else
+         memcpy(dp->text_ptr, chunks, dp->num_text * sizeof *chunks);
+   }
+
+   dp->text_stashed = 1; /* regardless of whether there are chunks or not */
+}
+
+#define text_stash(dp) if (!dp->text_stashed) text_stash(dp)
+
+static void
+text_restore(struct display *dp)
+{
+   /* libpng makes a copy, so this is fine: */
+   if (dp->text_ptr != NULL)
+      png_set_text(dp->write_pp, dp->ip, dp->text_ptr, dp->num_text);
+}
+
+#define text_restore(dp) if (dp->text_stashed) text_restore(dp)
+
+#else
+#define text_stash(dp) ((void)0)
+#define text_restore(dp) ((void)0)
+#endif /* pre 1.7 */
+
+/* OPTIONS:
+ *
+ * The command handles options of the forms:
+ *
+ *    --option
+ *       Turn an option on (Option)
+ *    --no-option
+ *       Turn an option off (Option)
+ *    --option=value
+ *       Set an option to a value (Value)
+ *    --option=val1,val2,val3
+ *       Set an option to a bitmask constructed from the values (List)
+ */
+static png_byte
+option_index(struct display *dp, const char *opt, size_t len)
+   /* Return the index (in options[]) of the given option, outputs an error if
+    * it does not exist.  Takes the name of the option and a length (number of
+    * characters in the name).
+    */
+{
+   png_byte j;
+
+   for (j=0; j<option_count; ++j)
+      if (strncmp(options[j].name, opt, len) == 0 && options[j].name[len] == 0)
+         return j;
+
+   /* If the setjmp buffer is set the code is asking for an option index; this
+    * is bad.  Otherwise this is the command line option parsing.
+    */
+   display_log(dp, dp->errset ? INTERNAL_ERROR : USER_ERROR,
+         "%.*s: unknown option", (int)/*SAFE*/len, opt);
+   abort(); /* NOT REACHED */
+}
+
+/* This works for an option name (no quotes): */
+#define OPTIND(dp, name) option_index(dp, #name, (sizeof #name)-1)
+
+static int
+get_option(struct display *dp, const char *opt, int *value)
+{
+   const png_byte i = option_index(dp, opt, strlen(opt));
+
+   if (dp->entry[i]) /* option was set on command line */
+   {
+      *value = dp->value[i];
+      return 1;
+   }
+
+   else
+      return 0;
+}
+
+static int
+set_opt_string_(struct display *dp, unsigned int sp, png_byte opt,
+      const char *entry_name)
+   /* Add the appropriate option string to dp->curr. */
+{
+   int offset, add;
+
+   if (sp > 0)
+      offset = dp->stack[sp-1].opt_string_end;
+
+   else
+      offset = dp->opt_string_start;
+
+   if (entry_name == range_lo)
+      add = sprintf(dp->curr+offset, " --%s=%d", options[opt].name,
+            dp->value[opt]);
+
+   else
+      add = sprintf(dp->curr+offset, " --%s=%s", options[opt].name, entry_name);
+
+   if (add < 0)
+      display_log(dp, INTERNAL_ERROR, "sprintf failed");
+
+   assert(offset+add < (int)/*SAFE*/sizeof dp->curr);
+   return offset+add;
+}
+
+static void
+set_opt_string(struct display *dp, unsigned int sp)
+   /* Add the appropriate option string to dp->curr. */
+{
+   dp->stack[sp].opt_string_end = set_opt_string_(dp, sp, dp->stack[sp].opt, 
+      options[dp->stack[sp].opt].values[dp->stack[sp].entry].name);
+}
+
+static void
+record_opt(struct display *dp, png_byte opt, const char *entry_name)
+   /* Record this option in dp->curr; called for an option not being searched,
+    * the caller passes in the name of the value, or range_lo to use the
+    * numerical value.
+    */
+{
+   const unsigned int sp = dp->csp; /* stack entry of next searched option */
+
+   if (sp >= dp->tsp)
+   {
+      /* At top of stack; add the opt string for this entry to the previous
+       * searched entry or the start of the dp->curr buffer if there is nothing
+       * on the stack yet (sp == 0).
+       */
+      const int offset = set_opt_string_(dp, sp, opt, entry_name);
+
+      if (sp > 0)
+         dp->stack[sp-1].opt_string_end = offset;
+
+      else
+         dp->opt_string_start = offset;
+   }
+
+   /* else do nothing: option already recorded */
+}
+
+static int
+opt_list_end(struct display *dp, png_byte opt, png_byte entry)
+{
+   if (options[opt].values[entry].name == range_lo)
+      return entry+1U >= options[opt].value_count /* missing range_hi */ ||
+         options[opt].values[entry+1U].name != range_hi /* likewise */ ||
+         options[opt].values[entry+1U].value <= dp->value[opt] /* range end */;
+
+   else
+      return entry+1U >= options[opt].value_count /* missing 'all' */ ||
+         options[opt].values[entry+1U].name == all /* last entry */;
+}
+
+static void
+push_opt(struct display *dp, unsigned int sp, png_byte opt, int search)
+   /* Push a new option onto the stack, initializing the new stack entry
+    * appropriately; this does all the work of next_opt (setting end/nsp) for
+    * the first entry in the list.
+    */
+{
+   png_byte entry;
+   const char *entry_name;
+
+   assert(sp == dp->tsp && sp < SL);
+
+   /* The starting entry is entry 0 unless there is a range in which case it is
+    * the entry corresponding to range_lo:
+    */
+   entry = options[opt].value_count;
+   assert(entry > 0U);
+
+   do
+   {
+      entry_name = options[opt].values[--entry].name;
+      if (entry_name == range_lo)
+         break;
+   }
+   while (entry > 0U);
+
+   dp->tsp = sp+1U;
+   dp->stack[sp].best_size =
+      dp->stack[sp].lo_size =
+      dp->stack[sp].hi_size = MAX_SIZE;
+
+   if (search && entry_name == range_lo) /* search this range */
+   {
+      dp->stack[sp].lo = options[opt].values[entry].value;
+      /* check for a mal-formed RANGE above: */
+      assert(entry+1 < options[opt].value_count &&
+             options[opt].values[entry+1].name == range_hi);
+      dp->stack[sp].hi = options[opt].values[entry+1].value;
+   }
+
+   else
+   {
+      /* next_opt will just iterate over the range. */
+      dp->stack[sp].lo = INT_MAX;
+      dp->stack[sp].hi = INT_MIN; /* Prevent range chop */
+   }
+
+   dp->stack[sp].opt = opt;
+   dp->stack[sp].entry = entry;
+   dp->stack[sp].best_val = dp->value[opt] = options[opt].values[entry].value;
+
+   set_opt_string(dp, sp);
+
+   /* This works for the search case too; if the range has only one entry 'end'
+    * will be marked here.
+    */
+   if (opt_list_end(dp, opt, entry))
+   {
+      dp->stack[sp].end = 1;
+      /* Skip the warning if pngcp did this itself.  See the code in
+       * set_windowBits_hi.
+       */
+      if (opt != dp->min_windowBits)
+         display_log(dp, APP_WARNING, "%s: only testing one value",
+               options[opt].name);
+   }
+
+   else
+   {
+      dp->stack[sp].end = 0;
+      dp->nsp = dp->tsp;
+   }
+
+   /* Do a lazy cache of the text chunks for libpng 1.6 and earlier; this is
+    * because they can only be written once(!) so if we are going to re-use the
+    * png_info we need a copy.
+    */
+   text_stash(dp);
+}
+
+static void
+next_opt(struct display *dp, unsigned int sp)
+   /* Return the next value for this option.  When called 'sp' is expected to be
+    * the topmost stack entry - only the topmost entry changes each time round -
+    * and there must be a valid entry to return.  next_opt will set dp->nsp to
+    * sp+1 if more entries are available, otherwise it will not change it and
+    * set dp->stack[s].end to true.
+    */
+{
+   int search = 0;
+   png_byte entry, opt;
+   const char *entry_name;
+
+   /* dp->stack[sp] must be the top stack entry and it must be active: */
+   assert(sp+1U == dp->tsp && !dp->stack[sp].end);
+
+   opt = dp->stack[sp].opt;
+   entry = dp->stack[sp].entry;
+   assert(entry+1U < options[opt].value_count);
+   entry_name = options[opt].values[entry].name;
+   assert(entry_name != NULL);
+
+   /* For ranges increment the value but don't change the entry, for all other
+    * cases move to the next entry and load its value:
+    */
+   if (entry_name == range_lo) /* a range */
+   {
+      /* A range can be iterated over or searched.  The default iteration option
+       * is indicated by hi < lo on the stack, otherwise the range being search
+       * is [lo..hi] (inclusive).
+       */
+      if (dp->stack[sp].lo > dp->stack[sp].hi)
+         dp->value[opt]++;
+
+      else
+      {
+         /* This is the best size found for this option value: */
+         png_alloc_size_t best_size = dp->stack[sp].best_size;
+         int lo = dp->stack[sp].lo;
+         int hi = dp->stack[sp].hi;
+         int val = dp->value[opt];
+
+         search = 1; /* end is determined here */
+         assert(best_size < MAX_SIZE);
+
+         if (val == lo)
+         {
+            /* Finding the best for the low end of the range: */
+            dp->stack[sp].lo_size = best_size;
+            assert(hi > val);
+
+            if (hi == val+1) /* only 2 entries */
+               dp->stack[sp].end = 1;
+
+            val = hi;
+         }
+
+         else if (val == hi)
+         {
+            dp->stack[sp].hi_size = best_size;
+            assert(val > lo+1); /* else 'end' set above */
+
+            if (val == lo+2) /* only three entries to test */
+               dp->stack[sp].end = 1;
+
+            val = (lo + val)/2;
+         }
+
+         else
+         {
+            png_alloc_size_t lo_size = dp->stack[sp].lo_size;
+            png_alloc_size_t hi_size = dp->stack[sp].hi_size;
+
+            /* lo and hi should have been tested. */
+            assert(lo_size < MAX_SIZE && hi_size < MAX_SIZE);
+
+            /* These cases arise with the 'probe' handling below when there is a
+             * dip or peak in the size curve.
+             */
+            if (val < lo) /* probing a new lo */
+            {
+               /* Swap lo and val: */
+               dp->stack[sp].lo = val;
+               dp->stack[sp].lo_size = best_size;
+               val = lo;
+               best_size = lo_size;
+               lo = dp->stack[sp].lo;
+               lo_size = dp->stack[sp].lo_size;
+            }
+
+            else if (val > hi) /* probing a new hi */
+            {
+               /* Swap hi and val: */
+               dp->stack[sp].hi = val;
+               dp->stack[sp].hi_size = best_size;
+               val = hi;
+               best_size = hi_size;
+               hi = dp->stack[sp].hi;
+               hi_size = dp->stack[sp].hi_size;
+            }
+
+            /* The following should be true or something got messed up above. */
+            assert(lo < val && val < hi);
+
+            /* If there are only four entries (lo, val, hi plus one more) just
+             * test the remaining entry.
+             */
+            if (hi == lo+3)
+            {
+               /* Because of the 'probe' code val can either be lo+1 or hi-1; we
+                * need to test the other.
+                */
+               val = lo + ((val == lo+1) ? 2 : 1);
+               assert(lo < val && val < hi);
+               dp->stack[sp].end = 1;
+            }
+
+            else
+            {
+               /* There are at least 2 entries still untested between lo and hi,
+                * i.e. hi >= lo+4.  'val' is the midpoint +/- 0.5
+                *
+                * Separate out the four easy cases when lo..val..hi are
+                * monotonically decreased or (more weird) increasing:
+                */
+               assert(hi > lo+3);
+
+               if (lo_size <= best_size && best_size <= hi_size)
+               {
+                  /* Select the low range; testing this first favours the low
+                   * range over the high range when everything comes out equal.
+                   * Because of the probing 'val' may be lo+1.  In that case end
+                   * the search and set 'val' to lo+2.
+                   */
+                  if (val == lo+1)
+                  {
+                     ++val;
+                     dp->stack[sp].end = 1;
+                  }
+
+                  else
+                  {
+                     dp->stack[sp].hi = hi = val;
+                     dp->stack[sp].hi_size = best_size;
+                     val = (lo + val) / 2;
+                  }
+               }
+
+               else if (lo_size >= best_size && best_size >= hi_size)
+               {
+                  /* Monotonically decreasing size; this is the expected case.
+                   * Select the high end of the range.  As above, val may be
+                   * hi-1.
+                   */
+                  if (val == hi-1)
+                  {
+                     --val;
+                     dp->stack[sp].end = 1;
+                  }
+
+                  else
+                  {
+                     dp->stack[sp].lo = lo = val;
+                     dp->stack[sp].lo_size = best_size;
+                     val = (val + hi) / 2;
+                  }
+               }
+
+               /* If both those tests failed 'best_size' is either greater than
+                * or less than both lo_size and hi_size.  There is a peak or dip
+                * in the curve of sizes from lo to hi and val is on the peak or
+                * dip.
+                *
+                * Because the ranges being searched as so small (level is 1..9,
+                * windowBits 8..15, memLevel 1..9) there will only be at most
+                * three untested values between lo..val and val..hi, so solve
+                * the problem by probing down from hi or up from lo, whichever
+                * is the higher.
+                *
+                * This is the place where 'val' is set to outside the range
+                * lo..hi, described as 'probing', though maybe 'narrowing' would
+                * be more accurate.
+                */
+               else if (lo_size <= hi_size) /* down from hi */
+               {
+                  dp->stack[sp].hi = val;
+                  dp->stack[sp].hi_size = best_size;
+                  val = --hi;
+               }
+
+               else /* up from low */
+               {
+                  dp->stack[sp].lo = val;
+                  dp->stack[sp].lo_size = best_size;
+                  val = ++lo;
+               }
+
+               /* lo and hi are still the true range limits, check for the end
+                * condition.
+                */
+               assert(hi > lo+1);
+               if (hi <= lo+2)
+                  dp->stack[sp].end = 1;
+            }
+         }
+
+         assert(val != dp->stack[sp].best_val); /* should be a new value */
+         dp->value[opt] = val;
+         dp->stack[sp].best_size = MAX_SIZE;
+      }
+   }
+
+   else
+   {
+      /* Increment 'entry' */
+      dp->value[opt] = options[opt].values[++entry].value;
+      dp->stack[sp].entry = entry;
+   }
+
+   set_opt_string(dp, sp);
+
+   if (!search && opt_list_end(dp, opt, entry)) /* end of list */
+      dp->stack[sp].end = 1;
+
+   else if (!dp->stack[sp].end) /* still active after all these tests */
+      dp->nsp = dp->tsp;
+}
+
+static int
+compare_option(const struct display *dp, unsigned int sp)
+{
+   int opt = dp->stack[sp].opt;
+
+   /* If the best so far is numerically less than the current value the
+    * current set of options is invariably worse.
+    */
+   if (dp->stack[sp].best_val < dp->value[opt])
+      return -1;
+
+   /* Lists of options are searched out of numerical order (currently only
+    * strategy), so only return +1 here when a range is being searched.
+    */
+   else if (dp->stack[sp].best_val > dp->value[opt])
+   {
+      if (dp->stack[sp].lo <= dp->stack[sp].hi /*searching*/)
+         return 1;
+
+      else
+         return -1;
+   }
+
+   else
+      return 0; /* match; current value is the best one */
+}
+
+static int
+advance_opt(struct display *dp, png_byte opt, int search)
+{
+   unsigned int sp = dp->csp++; /* my stack entry */
+
+   assert(sp >= dp->nsp); /* nsp starts off zero */
+
+   /* If the entry was active in the previous run dp->stack[sp] is already
+    * set up and dp->tsp will be greater than sp, otherwise a new entry
+    * needs to be created.
+    *
+    * dp->nsp is handled this way:
+    *
+    * 1) When an option is pushed onto the stack dp->nsp and dp->tsp are
+    *    both set (by push_opt) to the next stack entry *unless* there is
+    *    only one entry in the new list, in which case dp->stack[sp].end
+    *    is set.
+    *
+    * 2) For the top stack entry next_opt is called.  The entry must be
+    *    active (dp->stack[sp].end is not set) and either 'nsp' or 'end'
+    *    will be updated as appropriate.
+    *
+    * 3) For lower stack entries nsp is set unless the stack entry is
+    *    already at the end.  This means that when all the higher entries
+    *    are popped this entry will be too.
+    */
+   if (sp >= dp->tsp)
+   {
+      push_opt(dp, sp, opt, search); /* This sets tsp to sp+1 */
+      return 1; /* initialized */
+   }
+
+   else
+   {
+      int ret = 0; /* unchanged */
+
+      /* An option that is already on the stack; update best_size and best_val
+       * if appropriate.  On the first run there are no previous values and
+       * dp->write_size will be MAX_SIZE, however on the first run dp->tsp
+       * starts off as 0.
+       */
+      assert(dp->write_size > 0U && dp->write_size < MAX_SIZE);
+
+      if (dp->stack[sp].best_size > dp->write_size ||
+          (dp->stack[sp].best_size == dp->write_size &&
+           compare_option(dp, sp) > 0))
+      {
+         dp->stack[sp].best_size = dp->write_size;
+         dp->stack[sp].best_val = dp->value[opt];
+      }
+
+      if (sp+1U >= dp->tsp)
+      {
+         next_opt(dp, sp);
+         ret = 1; /* advanced */
+      }
+
+      else if (!dp->stack[sp].end) /* Active, not at top of stack */
+         dp->nsp = sp+1U;
+
+      return ret; /* advanced || unchanged */
+   }
+}
+
+static int
+getallopts_(struct display *dp, const png_byte opt, int *value, int record)
+   /* Like getop but iterate over all the values if the option was set to "all".
+    */
+{
+   if (dp->entry[opt]) /* option was set on command line */
+   {
+      /* Simple, single value, entries don't have a stack frame and have a fixed
+       * value (it doesn't change once set on the command line).  Otherwise the
+       * value (entry) selected from the command line is 'all':
+       */
+      const char *entry_name = options[opt].values[dp->entry[opt]-1].name;
+
+      if (entry_name == all)
+         (void)advance_opt(dp, opt, 0/*do not search; iterate*/);
+
+      else if (record)
+         record_opt(dp, opt, entry_name);
+
+      *value = dp->value[opt];
+      return 1; /* set */
+   }
+
+   else
+      return 0; /* not set */
+}
+
+static int
+getallopts(struct display *dp, const char *opt_str, int *value)
+{
+   return getallopts_(dp, option_index(dp, opt_str, strlen(opt_str)), value, 0);
+}
+
+static int
+getsearchopts(struct display *dp, const char *opt_str, int *value)
+   /* As above except that if the option was not set try a search */
+{
+   png_byte istrat;
+   const png_byte opt = option_index(dp, opt_str, strlen(opt_str));
+   int record = options[opt].search;
+   const char *entry_name;
+
+   /* If it was set on the command line honour the setting, including 'all'
+    * which will override the built in search:
+    */
+   if (getallopts_(dp, opt, value, record))
+      return 1;
+
+   else if (!record) /* not a search option */
+      return 0; /* unset and not searched */
+
+   /* Otherwise decide what to do here. */
+   istrat = OPTIND(dp, strategy);
+   entry_name = range_lo; /* record the value, not the name */
+
+   if (opt == istrat) /* search all strategies */
+      (void)advance_opt(dp, opt, 0/*iterate*/), record=0;
+
+   else if (opt == OPTIND(dp, level))
+   {
+      /* Both RLE and HUFFMAN don't benefit from level increases */
+      if (dp->value[istrat] == Z_RLE || dp->value[istrat] == Z_HUFFMAN_ONLY)
+         dp->value[opt] = 1;
+
+      else /* fixed, filtered or default */
+         (void)advance_opt(dp, opt, 1/*search*/), record=0;
+   }
+
+   else if (opt == OPTIND(dp, windowBits))
+   {
+      /* Changing windowBits for strategies that do not search the window is
+       * pointless.  Huffman-only does not search, RLE only searches backwards
+       * one byte, so given that the maximum string length is 258, a windowBits
+       * of 9 is always sufficient.
+       */
+      if (dp->value[istrat] == Z_HUFFMAN_ONLY)
+         dp->value[opt] = 8;
+
+      else if (dp->value[istrat] == Z_RLE)
+         dp->value[opt] = 9;
+
+      else /* fixed, filtered or default */
+         (void)advance_opt(dp, opt, 1/*search*/), record=0;
+   }
+
+   else if (opt == OPTIND(dp, memLevel))
+   {
+#     if 0
+         (void)advance_opt(dp, opt, 0/*all*/), record=0;
+#     else
+         dp->value[opt] = MAX_MEM_LEVEL;
+#     endif
+   }
+
+   else /* something else */
+      assert(0=="reached");
+
+   if (record)
+      record_opt(dp, opt, entry_name);
+
+   /* One of the above searched options: */
+   *value = dp->value[opt];
+   return 1;
+}
+
+static int
+find_val(struct display *dp, png_byte opt, const char *str, size_t len)
+   /* Like option_index but sets (index+i) of the entry in options[opt] that
+    * matches str[0..len-1] into dp->entry[opt] as well as returning the actual
+    * value.
+    */
+{
+   int rlo = INT_MAX, rhi = INT_MIN;
+   png_byte j, irange = 0;
+
+   for (j=1U; j<=options[opt].value_count; ++j)
+   {
+      if (strncmp(options[opt].values[j-1U].name, str, len) == 0 &&
+          options[opt].values[j-1U].name[len] == 0)
+      {
+         dp->entry[opt] = j;
+         return options[opt].values[j-1U].value;
+      }
+      else if (options[opt].values[j-1U].name == range_lo)
+         rlo = options[opt].values[j-1U].value, irange = j;
+      else if (options[opt].values[j-1U].name == range_hi)
+         rhi = options[opt].values[j-1U].value;
+   }
+
+   /* No match on the name, but there may be a range. */
+   if (irange > 0)
+   {
+      char *ep = NULL;
+      long l = strtol(str, &ep, 0);
+
+      if (ep == str+len && l >= rlo && l <= rhi)
+      {
+         dp->entry[opt] = irange; /* range_lo */
+         return (int)/*SAFE*/l;
+      }
+   }
+
+   display_log(dp, dp->errset ? INTERNAL_ERROR : USER_ERROR,
+         "%s: unknown value setting '%.*s'", options[opt].name,
+         (int)/*SAFE*/len, str);
+   abort(); /* NOT REACHED */
+}
+
+static int
+opt_check(struct display *dp, const char *arg)
+{
+   assert(dp->errset == 0);
+
+   if (arg != NULL && arg[0] == '-' && arg[1] == '-')
+   {
+      int i = 0, negate = (strncmp(arg+2, "no-", 3) == 0), val;
+      png_byte j;
+
+      if (negate)
+         arg += 5; /* --no- */
+
+      else
+         arg += 2; /* -- */
+
+      /* Find the length (expect arg\0 or arg=) */
+      while (arg[i] != 0 && arg[i] != '=') ++i;
+
+      /* So arg[0..i-1] is the argument name, this does not return if this isn't
+       * a valid option name.
+       */
+      j = option_index(dp, arg, i);
+
+      /* It matcheth an option; check the remainder. */
+      if (arg[i] == 0) /* no specified value, use the default */
+      {
+         val = options[j].values[negate].value;
+         dp->entry[j] = (png_byte)/*SAFE*/(negate + 1U);
+      }
+
+      else
+      {
+         const char *list = arg + (i+1);
+
+         /* Expect a single value here unless this is a list, in which case
+          * multiple values are combined.
+          */
+         if (options[j].opt != LIST)
+         {
+            /* find_val sets 'dp->entry[j]' to a non-zero value: */
+            val = find_val(dp, j, list, strlen(list));
+
+            if (negate)
+            {
+               if (options[j].opt < OPTION)
+                  val = !val;
+
+               else
+               {
+                  display_log(dp, USER_ERROR,
+                        "%.*s: option=arg cannot be negated", i, arg);
+                  abort(); /* NOT REACHED */
+               }
+            }
+         }
+
+         else /* multiple options separated by ',' characters */
+         {
+            /* --no-option negates list values from the default, which should
+             * therefore be 'all'.  Notice that if the option list is empty in
+             * this case nothing will be removed and therefore --no-option= is
+             * the same as --option.
+             */
+            if (negate)
+               val = options[j].values[0].value;
+
+            else
+               val = 0;
+
+            while (*list != 0) /* allows option= which sets 0 */
+            {
+               /* A value is terminated by the end of the list or a ','
+                * character.
+                */
+               int v, iv;
+
+               iv = 0; /* an index into 'list' */
+               while (list[++iv] != 0 && list[iv] != ',') {}
+
+               v = find_val(dp, j, list, iv);
+
+               if (negate)
+                  val &= ~v;
+
+               else
+                  val |= v;
+
+               list += iv;
+               if (*list != 0)
+                  ++list; /* skip the ',' */
+            }
+         }
+      }
+
+      /* 'val' is the new value, store it for use later and debugging: */
+      dp->value[j] = val;
+
+      if (options[j].opt < LEVEL_MASK)
+      {
+         /* The handling for error levels is to set the level. */
+         if (val) /* Set this level */
+            dp->options = (dp->options & ~LEVEL_MASK) | options[j].opt;
+
+         else
+            display_log(dp, USER_ERROR,
+      "%.*s: messages cannot be turned off individually; set a message level",
+                  i, arg);
+      }
+
+      else if (options[j].opt < OPTION)
+      {
+         if (val)
+            dp->options |= options[j].opt;
+
+         else
+            dp->options &= ~options[j].opt;
+      }
+
+      return 1; /* this is an option */
+   }
+
+   else
+      return 0; /* not an option */
+}
+
+#ifdef PNG_PNGCP_TIMING_SUPPORTED
+static void
+set_timer(struct display *dp, struct timespec *timer)
+{
+   /* Do the timing using clock_gettime and the per-process timer. */
+   if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, timer))
+   {
+      display_log(dp, APP_ERROR,
+            "CLOCK_PROCESS_CPUTIME_ID: %s: timing disabled\n", strerror(errno));
+      dp->value[OPTIND(dp,time)] = 0; /* i.e. off */
+   }
+}
+
+static void
+start_timer(struct display *dp, int what)
+{
+   if ((dp->value[OPTIND(dp,time)] & what) != 0)
+      set_timer(dp, what == PNGCP_TIME_READ ? &dp->read_time : &dp->write_time);
+}
+
+static void
+end_timer(struct display *dp, int what)
+{
+   if ((dp->value[OPTIND(dp,time)] & what) != 0)
+   {
+      struct timespec t, tmp;
+
+      set_timer(dp, &t);
+
+      if (what == PNGCP_TIME_READ)
+         tmp = dp->read_time;
+
+      else
+         tmp = dp->write_time;
+
+      t.tv_sec -= tmp.tv_sec;
+      t.tv_nsec -= tmp.tv_nsec;
+
+      if (t.tv_nsec < 0)
+      {
+         --(t.tv_sec);
+         t.tv_nsec += 1000000000L;
+      }
+
+      if (what == PNGCP_TIME_READ)
+         dp->read_time = t, tmp = dp->read_time_total;
+
+      else
+         dp->write_time = t, tmp = dp->write_time_total;
+
+      tmp.tv_sec += t.tv_sec;
+      tmp.tv_nsec += t.tv_nsec;
+
+      if (tmp.tv_nsec >= 1000000000L)
+      {
+         ++(tmp.tv_sec);
+         tmp.tv_nsec -= 1000000000L;
+      }
+
+      if (what == PNGCP_TIME_READ)
+         dp->read_time_total = tmp;
+
+      else
+         dp->write_time_total = tmp;
+   }
+}
+
+static void
+print_time(const char *what, struct timespec t)
+{
+   printf("%s %.2lu.%.9ld", what, (unsigned long)t.tv_sec, t.tv_nsec);
+}
+#else /* !PNGCP_TIMING */
+#define start_timer(dp, what) ((void)0)
+#define end_timer(dp, what) ((void)0)
+#endif /* !PNGCP_TIMING */
+
+/* The following is used in main to verify that the final argument is a
+ * directory:
+ */
+static int
+checkdir(const char *pathname)
+{
+   struct stat buf;
+   return stat(pathname, &buf) == 0 && S_ISDIR(buf.st_mode);
+}
+
+/* Work out whether a path is valid (if not a display_log occurs), a directory
+ * (1 is returned) or a file *or* non-existent (0 is returned).
+ *
+ * Used for a write path.
+ */
+static int
+isdir(struct display *dp, const char *pathname)
+{
+   if (pathname == NULL)
+      return 0; /* stdout */
+
+   else if (pathname[0] == 0)
+      return 1; /* empty string */
+
+   else
+   {
+      struct stat buf;
+      int ret = stat(pathname, &buf);
+
+      if (ret == 0) /* the entry exists */
+      {
+         if (S_ISDIR(buf.st_mode))
+            return 1;
+
+         /* Else expect an object that exists and can be written: */
+         if (access(pathname, W_OK) != 0)
+            display_log(dp, USER_ERROR, "%s: cannot be written (%s)", pathname,
+                  strerror(errno));
+
+         return 0; /* file (exists, can be written) */
+      }
+
+      else /* an error */
+      {
+         /* Non-existence is fine, other errors are not: */
+         if (errno != ENOENT)
+            display_log(dp, USER_ERROR, "%s: invalid output name (%s)",
+                  pathname, strerror(errno));
+
+         return 0; /* file (does not exist) */
+      }
+   }
+}
+
+static void
+makename(struct display *dp, const char *dir, const char *infile)
+{
+   /* Make a name for an output file (and check it). */
+   dp->namebuf[0] = 0;
+
+   if (dir == NULL || infile == NULL)
+      display_log(dp, INTERNAL_ERROR, "NULL name to makename");
+
+   else
+   {
+      size_t dsize = strlen(dir);
+
+      if (dsize <= (sizeof dp->namebuf)-2) /* Allow for name + '/' + '\0' */
+      {
+         size_t isize = strlen(infile);
+         size_t istart = isize-1;
+
+         /* This should fail before here: */
+         if (infile[istart] == '/')
+            display_log(dp, INTERNAL_ERROR, "infile with trailing /");
+
+         memcpy(dp->namebuf, dir, dsize);
+         if (dsize > 0 && dp->namebuf[dsize-1] != '/')
+            dp->namebuf[dsize++] = '/';
+
+         /* Find the rightmost non-/ character: */
+         while (istart > 0 && infile[istart-1] != '/')
+            --istart;
+
+         isize -= istart;
+         infile += istart;
+
+         if (dsize+isize < (sizeof dp->namebuf)) /* dsize + infile + '\0' */
+         {
+            memcpy(dp->namebuf+dsize, infile, isize+1);
+
+            if (isdir(dp, dp->namebuf))
+               display_log(dp, USER_ERROR, "%s: output file is a directory",
+                     dp->namebuf);
+         }
+
+         else
+         {
+            dp->namebuf[dsize] = 0; /* allowed for: -2 at start */
+            display_log(dp, USER_ERROR, "%s%s: output file name too long",
+                  dp->namebuf, infile);
+         }
+      }
+
+      else
+         display_log(dp, USER_ERROR, "%s: output directory name too long", dir);
+   }
+}
+
+/* error handler callbacks for libpng */
+static void PNGCBAPI
+display_warning(png_structp pp, png_const_charp warning)
+{
+   struct display *dp = get_dp(pp);
+
+   /* This is used to prevent repeated warnings while searching */
+   if (!dp->no_warnings)
+      display_log(get_dp(pp), LIBPNG_WARNING, "%s", warning);
+}
+
+static void PNGCBAPI
+display_error(png_structp pp, png_const_charp error)
+{
+   struct display *dp = get_dp(pp);
+
+   display_log(dp, LIBPNG_ERROR, "%s", error);
+}
+
+static void
+display_start_read(struct display *dp, const char *filename)
+{
+   if (filename != NULL)
+   {
+      dp->filename = filename;
+      dp->fp = fopen(filename, "rb");
+   }
+
+   else
+   {
+      dp->filename = "<stdin>";
+      dp->fp = stdin;
+   }
+
+   dp->w = dp->h = 0U;
+   dp->bpp = 0U;
+   dp->size = 0U;
+   dp->read_size = 0U;
+
+   if (dp->fp == NULL)
+      display_log(dp, USER_ERROR, "file open failed (%s)", strerror(errno));
+}
+
+static void PNGCBAPI
+read_function(png_structp pp, png_bytep data, png_size_t size)
+{
+   struct display *dp = get_dp(pp);
+
+   if (size == 0U || fread(data, size, 1U, dp->fp) == 1U)
+      dp->read_size += size;
+
+   else
+   {
+      if (feof(dp->fp))
+         display_log(dp, LIBPNG_ERROR, "PNG file truncated");
+      else
+         display_log(dp, LIBPNG_ERROR, "PNG file read failed (%s)",
+               strerror(errno));
+   }
+}
+
+static void
+read_png(struct display *dp, const char *filename)
+{
+   display_clean_read(dp); /* safety */
+   display_start_read(dp, filename);
+
+   dp->read_pp = png_create_read_struct(PNG_LIBPNG_VER_STRING, dp,
+      display_error, display_warning);
+   if (dp->read_pp == NULL)
+      display_log(dp, LIBPNG_ERROR, "failed to create read struct");
+
+#  ifdef PNG_BENIGN_ERRORS_SUPPORTED
+      png_set_benign_errors(dp->read_pp, 1/*allowed*/);
+#  endif /* BENIGN_ERRORS */
+
+#  ifdef FIX_INDEX
+      if ((dp->options & FIX_INDEX) != 0)
+         png_set_check_for_invalid_index(dp->read_pp, 1/*on, no warning*/);
+#     ifdef IGNORE_INDEX
+         else
+#     endif /* IGNORE_INDEX */
+#  endif /* FIX_INDEX */
+#  ifdef IGNORE_INDEX
+      if ((dp->options & IGNORE_INDEX) != 0) /* DANGEROUS */
+         png_set_check_for_invalid_index(dp->read_pp, -1/*off completely*/);
+#  endif /* IGNORE_INDEX */
+
+   /* The png_read_png API requires us to make the info struct, but it does the
+    * call to png_read_info.
+    */
+   dp->ip = png_create_info_struct(dp->read_pp);
+   if (dp->ip == NULL)
+      png_error(dp->read_pp, "failed to create info struct");
+
+   /* Set the IO handling */
+   png_set_read_fn(dp->read_pp, dp, read_function);
+
+#  ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
+      png_set_keep_unknown_chunks(dp->read_pp, PNG_HANDLE_CHUNK_ALWAYS, NULL,
+            0);
+#  endif /* HANDLE_AS_UNKNOWN */
+
+#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
+      /* Remove the user limits, if any */
+      png_set_user_limits(dp->read_pp, 0x7fffffff, 0x7fffffff);
+#  endif /* SET_USER_LIMITS */
+
+   /* Now read the PNG. */
+   start_timer(dp, PNGCP_TIME_READ);
+   png_read_png(dp->read_pp, dp->ip, 0U/*transforms*/, NULL/*params*/);
+   end_timer(dp, PNGCP_TIME_READ);
+   dp->w = png_get_image_width(dp->read_pp, dp->ip);
+   dp->h = png_get_image_height(dp->read_pp, dp->ip);
+   dp->ct = png_get_color_type(dp->read_pp, dp->ip);
+   dp->bpp = png_get_bit_depth(dp->read_pp, dp->ip) *
+             png_get_channels(dp->read_pp, dp->ip);
+   {
+      /* png_get_rowbytes should never return 0 because the value is set by the
+       * first call to png_set_IHDR, which should have happened by now, but just
+       * in case:
+       */
+      png_alloc_size_t rb = png_get_rowbytes(dp->read_pp, dp->ip);
+
+      if (rb == 0)
+         png_error(dp->read_pp, "invalid row byte count from libpng");
+
+      /* The size calc can overflow. */
+      if ((MAX_SIZE-dp->h)/rb < dp->h)
+         png_error(dp->read_pp, "image too large");
+
+      dp->size = rb * dp->h + dp->h/*filter byte*/;
+   }
+
+#ifdef FIX_INDEX
+   if (dp->ct == PNG_COLOR_TYPE_PALETTE && (dp->options & FIX_INDEX) != 0)
+   {
+      int max = png_get_palette_max(dp->read_pp, dp->ip);
+      png_colorp palette = NULL;
+      int num = -1;
+
+      if (png_get_PLTE(dp->read_pp, dp->ip, &palette, &num) != PNG_INFO_PLTE
+          || max < 0 || num <= 0 || palette == NULL)
+         display_log(dp, LIBPNG_ERROR, "invalid png_get_PLTE result");
+
+      if (max >= num)
+      {
+         /* 'Fix' the palette. */
+         int i;
+         png_color newpal[256];
+
+         for (i=0; i<num; ++i)
+            newpal[i] = palette[i];
+
+         /* Fill in any remainder with a warning color: */
+         for (; i<=max; ++i)
+         {
+            newpal[i].red = 0xbe;
+            newpal[i].green = 0xad;
+            newpal[i].blue = 0xed;
+         }
+
+         png_set_PLTE(dp->read_pp, dp->ip, newpal, i);
+      }
+   }
+#endif /* FIX_INDEX */
+
+   display_clean_read(dp);
+   dp->operation = "none";
+}
+
+static void
+display_start_write(struct display *dp, const char *filename)
+{
+   assert(dp->fp == NULL);
+
+   if ((dp->options & NOWRITE) != 0)
+      dp->output_file = "<no write>";
+
+   else
+   {
+      if (filename != NULL)
+      {
+         dp->output_file = filename;
+         dp->fp = fopen(filename, "wb");
+      }
+
+      else
+      {
+         dp->output_file = "<stdout>";
+         dp->fp = stdout;
+      }
+
+      if (dp->fp == NULL)
+         display_log(dp, USER_ERROR, "%s: file open failed (%s)",
+               dp->output_file, strerror(errno));
+   }
+}
+
+static void PNGCBAPI
+write_function(png_structp pp, png_bytep data, png_size_t size)
+{
+   struct display *dp = get_dp(pp);
+
+   /* The write fail is classed as a USER_ERROR, so --quiet does not turn it
+    * off, this seems more likely to be correct.
+    */
+   if (dp->fp == NULL || fwrite(data, size, 1U, dp->fp) == 1U)
+   {
+      dp->write_size += size;
+      if (dp->write_size < size || dp->write_size == MAX_SIZE)
+         png_error(pp, "IDAT size overflow");
+   }
+
+   else
+      display_log(dp, USER_ERROR, "%s: PNG file write failed (%s)",
+            dp->output_file, strerror(errno));
+}
+
+/* Compression option, 'method' is never set: there is no choice.
+ *
+ * IMPORTANT: the order of the entries in this macro determines the preference
+ * order when two different combos of two of these options produce an IDAT of
+ * the same size.  The logic here is to put the things that affect the decoding
+ * of the PNG image ahead of those that are relevant only to the encoding.
+ */
+#define SET_COMPRESSION\
+   SET(strategy, strategy);\
+   SET(windowBits, window_bits);\
+   SET(level, level);\
+   SET(memLevel, mem_level);
+
+#ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
+static void
+search_compression(struct display *dp)
+{
+   /* Like set_compression below but use a more restricted search than 'all' */
+   int val;
+
+#  define SET(name, func) if (getsearchopts(dp, #name, &val))\
+      png_set_compression_ ## func(dp->write_pp, val);
+   SET_COMPRESSION
+#  undef SET
+}
+
+static void
+set_compression(struct display *dp)
+{
+   int val;
+
+#  define SET(name, func) if (getallopts(dp, #name, &val))\
+      png_set_compression_ ## func(dp->write_pp, val);
+   SET_COMPRESSION
+#  undef SET
+}
+
+#ifdef PNG_SW_COMPRESS_level /* 1.7.0+ */
+static void
+set_ICC_profile_compression(struct display *dp)
+{
+   int val;
+
+#  define SET(name, func) if (getallopts(dp, "ICC-profile-" #name, &val))\
+      png_set_ICC_profile_compression_ ## func(dp->write_pp, val);
+   SET_COMPRESSION
+#  undef SET
+}
+#else
+#  define set_ICC_profile_compression(dp) ((void)0)
+#endif
+#else
+#  define search_compression(dp) ((void)0)
+#  define set_compression(dp) ((void)0)
+#  define set_ICC_profile_compression(dp) ((void)0)
+#endif /* WRITE_CUSTOMIZE_COMPRESSION */
+
+#ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
+static void
+set_text_compression(struct display *dp)
+{
+   int val;
+
+#  define SET(name, func) if (getallopts(dp, "text-" #name, &val))\
+      png_set_text_compression_ ## func(dp->write_pp, val);
+   SET_COMPRESSION
+#  undef SET
+}
+#else
+#  define set_text_compression(dp) ((void)0)
+#endif /* WRITE_CUSTOMIZE_ZTXT_COMPRESSION */
+
+static void
+write_png(struct display *dp, const char *destname)
+{
+   display_clean_write(dp); /* safety */
+   display_start_write(dp, destname);
+
+   dp->write_pp = png_create_write_struct(PNG_LIBPNG_VER_STRING, dp,
+      display_error, display_warning);
+
+   if (dp->write_pp == NULL)
+      display_log(dp, LIBPNG_ERROR, "failed to create write png_struct");
+
+#  ifdef PNG_BENIGN_ERRORS_SUPPORTED
+      png_set_benign_errors(dp->write_pp, 1/*allowed*/);
+#  endif /* BENIGN_ERRORS */
+
+   png_set_write_fn(dp->write_pp, dp, write_function, NULL/*flush*/);
+
+#ifdef IGNORE_INDEX
+   if ((dp->options & IGNORE_INDEX) != 0) /* DANGEROUS */
+      png_set_check_for_invalid_index(dp->write_pp, -1/*off completely*/);
+#endif /* IGNORE_INDEX */
+
+   /* Restore the text chunks when using libpng 1.6 or less; this is a macro
+    * which expands to nothing in 1.7+  In earlier versions it tests
+    * dp->text_stashed, which is only set (below) *after* the first write.
+    */
+   text_restore(dp);
+
+#  ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
+      png_set_keep_unknown_chunks(dp->write_pp, PNG_HANDLE_CHUNK_ALWAYS, NULL,
+            0);
+#  endif /* HANDLE_AS_UNKNOWN */
+
+#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
+      /* Remove the user limits, if any */
+      png_set_user_limits(dp->write_pp, 0x7fffffff, 0x7fffffff);
+#  endif
+
+   /* OPTION HANDLING */
+   /* compression outputs, IDAT and zTXt/iTXt: */
+   dp->tsp = dp->nsp;
+   dp->nsp = dp->csp = 0;
+#  ifdef PNG_SW_COMPRESS_png_level
+      {
+         int val;
+
+         /* This sets everything, but then the following options just override
+          * the specific settings for ICC profiles and text.
+          */
+         if (getallopts(dp, "compression", &val))
+            png_set_compression(dp->write_pp, val);
+
+         if (getallopts(dp, "ICC-profile-compression", &val))
+            png_set_ICC_profile_compression(dp->write_pp, val);
+
+         if (getallopts(dp, "text-compression", &val))
+            png_set_text_compression(dp->write_pp, val);
+      }
+#  endif /* png_level support */
+   if (dp->options & SEARCH)
+      search_compression(dp);
+   else
+      set_compression(dp);
+   set_ICC_profile_compression(dp);
+   set_text_compression(dp);
+
+   {
+      int val;
+
+      /* The permitted range is 1..0x7FFFFFFF, so the cast is safe */
+      if (get_option(dp, "IDAT-size", &val))
+         png_set_IDAT_size(dp->write_pp, val);
+   }
+
+   /* filter handling */
+#  ifdef PNG_WRITE_FILTER_SUPPORTED
+      {
+         int val;
+
+         if (get_option(dp, "filter", &val))
+            png_set_filter(dp->write_pp, PNG_FILTER_TYPE_BASE, val);
+      }
+#  endif /* WRITE_FILTER */
+
+   /* This just uses the 'read' info_struct directly, it contains the image. */
+   dp->write_size = 0U;
+   start_timer(dp, PNGCP_TIME_WRITE);
+   png_write_png(dp->write_pp, dp->ip, 0U/*transforms*/, NULL/*params*/);
+   end_timer(dp, PNGCP_TIME_WRITE);
+
+   /* Make sure the file was written ok: */
+   if (dp->fp != NULL)
+   {
+      FILE *fp = dp->fp;
+      dp->fp = NULL;
+      if (fclose(fp))
+         display_log(dp, APP_ERROR, "%s: write failed (%s)",
+               destname == NULL ? "stdout" : destname, strerror(errno));
+   }
+
+   /* Clean it on the way out - if control returns to the caller then the
+    * written_file contains the required data.
+    */
+   display_clean_write(dp);
+   dp->operation = "none";
+}
+
+static void
+set_windowBits_hi(struct display *dp)
+{
+   /* windowBits is in the range 8..15 but zlib maps '8' to '9' so it is only
+    * worth using if the data size is 256 byte or less.
+    */
+   int wb = MAX_WBITS; /* for large images */
+   int i = VLSIZE(windowBits_IDAT);
+
+   while (wb > 8 && dp->size <= 1U<<(wb-1)) --wb;
+
+   while (--i >= 0) if (VLNAME(windowBits_IDAT)[i].name == range_hi) break;
+
+   assert(i > 1); /* vl_windowBits_IDAT always has a RANGE() */
+   VLNAME(windowBits_IDAT)[i].value = wb;
+
+   assert(VLNAME(windowBits_IDAT)[--i].name == range_lo);
+   VLNAME(windowBits_IDAT)[i].value = wb > 8 ? 9 : 8;
+
+   /* If wb == 8 then any search has been restricted to just one windowBits
+    * entry.  Record that here to avoid producing a spurious app-level warning
+    * above.
+    */
+   if (wb == 8)
+      dp->min_windowBits = OPTIND(dp, windowBits);
+}
+
+static int
+better_options(const struct display *dp)
+{
+   /* Are these options better than the best found so far?  Normally the
+    * options are tested in preference order, best first, however when doing a
+    * search operation on a range the range values are tested out of order.  In
+    * that case preferable options will get tested later.
+    *
+    * This function looks through the stack from the bottom up looking for an
+    * option that does not match the current best value.  When it finds one it
+    * checks to see if it is more or less desireable and returns true or false
+    * as appropriate.
+    *
+    * Notice that this means that the order options are pushed onto the stack
+    * conveys a priority; lower/earlier options are more important than later
+    * ones.
+    */
+   unsigned int sp;
+
+   for (sp=0; sp<dp->csp; ++sp)
+   {
+      int c = compare_option(dp, sp);
+
+      if (c < 0)
+         return 0; /* worse */
+
+      else if (c > 0)
+         return 1; /* better */
+   }
+
+   assert(0 && "unreached");
+}
+
+static void
+print_search_results(struct display *dp)
+{
+   assert(dp->filename != NULL);
+   printf("%s [%ld x %ld %d bpp %s, %lu bytes] %lu -> %lu with '%s'\n",
+      dp->filename, (unsigned long)dp->w, (unsigned long)dp->h, dp->bpp,
+      cts(dp->ct), (unsigned long)dp->size, (unsigned long)dp->read_size,
+      (unsigned long)dp->best_size, dp->best);
+   fflush(stdout);
+}
+
+static void
+log_search(struct display *dp, unsigned int log_depth)
+{
+   /* Log, and reset, the search so far: */
+   if (dp->nsp/*next entry to change*/ <= log_depth)
+   {
+      print_search_results(dp);
+      /* Start again with this entry: */
+      dp->best_size = MAX_SIZE;
+   }
+}
+
+static void
+cp_one_file(struct display *dp, const char *filename, const char *destname)
+{
+   unsigned int log_depth;
+
+   dp->filename = filename;
+   dp->operation = "read";
+   dp->no_warnings = 0;
+
+   /* Read it then write it: */
+   if (filename != NULL && access(filename, R_OK) != 0)
+      display_log(dp, USER_ERROR, "%s: invalid file name (%s)",
+            filename, strerror(errno));
+
+   read_png(dp, filename);
+
+   /* But 'destname' may be a directory. */
+   dp->operation = "write";
+
+   /* Limit the upper end of the windowBits range for this file */
+   set_windowBits_hi(dp);
+
+   /* For logging, depth to log: */
+   {
+      int val;
+
+      if (get_option(dp, "log-depth", &val) && val >= 0)
+         log_depth = (unsigned int)/*SAFE*/val;
+
+      else
+         log_depth = 0U;
+   }
+
+   if (destname != NULL) /* else stdout */
+   {
+      if (isdir(dp, destname))
+      {
+         makename(dp, destname, filename);
+         destname = dp->namebuf;
+      }
+
+      else if (access(destname, W_OK) != 0 && errno != ENOENT)
+         display_log(dp, USER_ERROR, "%s: invalid output name (%s)", destname,
+               strerror(errno));
+   }
+
+   dp->nsp = 0;
+   dp->curr[0] = 0; /* acts as a flag for the caller */
+   dp->opt_string_start = 0;
+   dp->best[0] = 0; /* safety */
+   dp->best_size = MAX_SIZE;
+   write_png(dp, destname);
+
+   /* Initialize the 'best' fields: */
+   strcpy(dp->best, dp->curr);
+   dp->best_size = dp->write_size;
+
+   if (dp->nsp > 0) /* interating over lists */
+   {
+      char *tmpname, tmpbuf[(sizeof dp->namebuf) + 4];
+      assert(dp->curr[0] == ' ' && dp->tsp > 0);
+
+      /* Cancel warnings on subsequent writes */
+      log_search(dp, log_depth);
+      dp->no_warnings = 1;
+
+      /* Make a temporary name for the subsequent tests: */
+      if (destname != NULL)
+      {
+         strcpy(tmpbuf, destname);
+         strcat(tmpbuf, ".tmp"); /* space for .tmp allocated above */
+         tmpname = tmpbuf;
+      }
+
+      else
+         tmpname = NULL; /* stdout */
+
+      /* Loop to find the best option. */
+      do
+      {
+         write_png(dp, tmpname);
+
+         /* And compare the sizes (the write function makes sure write_size
+          * doesn't overflow.)
+          */
+         assert(dp->csp > 0);
+
+         if (dp->write_size < dp->best_size ||
+             (dp->write_size == dp->best_size && better_options(dp)))
+         {
+            if (destname != NULL && rename(tmpname, destname) != 0)
+               display_log(dp, APP_ERROR, "rename %s %s failed (%s)", tmpname,
+                     destname, strerror(errno));
+
+            strcpy(dp->best, dp->curr);
+            dp->best_size = dp->write_size;
+         }
+
+         else if (tmpname != NULL && unlink(tmpname) != 0)
+            display_log(dp, APP_WARNING, "unlink %s failed (%s)", tmpname,
+                  strerror(errno));
+
+         log_search(dp, log_depth);
+      }
+      while (dp->nsp > 0);
+
+      /* Do this for the 'sizes' option so that it reports the correct size. */
+      dp->write_size = dp->best_size;
+   }
+}
+
+static int
+cppng(struct display *dp, const char *file, const char *gv dest)
+   /* Exists solely to isolate the setjmp clobbers which some versions of GCC
+    * erroneously generate.
+    */
+{
+   int ret = setjmp(dp->error_return);
+
+   if (ret == 0)
+   {
+      dp->errset = 1;
+      cp_one_file(dp, file, dest);
+      dp->errset = 0;
+      return 0;
+   }
+
+   else
+   {
+      dp->errset = 0;
+
+      if (ret < ERRORS) /* shouldn't longjmp on warnings */
+         display_log(dp, INTERNAL_ERROR, "unexpected return code %d", ret);
+
+      return ret;
+   }
+}
+
+int
+main(const int argc, const char * const * const argv)
+{
+   /* For each file on the command line test it with a range of transforms */
+   int option_end;
+   struct display d;
+
+   display_init(&d);
+
+   d.operation = "options";
+   for (option_end = 1;
+        option_end < argc && opt_check(&d, argv[option_end]);
+        ++option_end)
+   {
+   }
+
+   /* Do a quick check on the directory target case; when there are more than
+    * two arguments the last one must be a directory.
+    */
+   if (!(d.options & NOWRITE) && option_end+2 < argc && !checkdir(argv[argc-1]))
+   {
+      fprintf(stderr,
+            "pngcp: %s: directory required with more than two arguments\n",
+            argv[argc-1]);
+      return 99;
+   }
+
+   {
+      int errors = 0;
+      int i = option_end;
+
+      /* Do this at least once; if there are no arguments stdin/stdout are used.
+       */
+      d.operation = "files";
+      do
+      {
+         const char *infile = NULL;
+         const char *outfile = NULL;
+         int ret;
+
+         if (i < argc)
+         {
+            infile = argv[i++];
+            if (!(d.options & NOWRITE) && i < argc)
+               outfile = argv[argc-1];
+         }
+
+         ret = cppng(&d, infile, outfile);
+
+         if (ret)
+         {
+            if (ret > QUIET) /* abort on user or internal error */
+               return 99;
+
+            /* An error: the output is meaningless */
+         }
+
+         else if (d.best[0] != 0)
+         {
+            /* This result may already have been output, in which case best_size
+             * has been reset.
+             */
+            if (d.best_size < MAX_SIZE)
+               print_search_results(&d);
+         }
+
+         else if (d.options & SIZES)
+         {
+            printf("%s [%ld x %ld %d bpp %s, %lu bytes] %lu -> %lu [0x%lx]\n",
+                  infile, (unsigned long)d.w, (unsigned long)d.h, d.bpp,
+                  cts(d.ct), (unsigned long)d.size, (unsigned long)d.read_size,
+                  (unsigned long)d.write_size, (unsigned long)d.results);
+            fflush(stdout);
+         }
+
+         /* Here on any return, including failures, except user/internal issues
+          */
+         {
+            const int pass = (d.options & STRICT) ?
+               RESULT_STRICT(d.results) : RESULT_RELAXED(d.results);
+
+            if (!pass)
+               ++errors;
+
+            if (d.options & LOG)
+            {
+               int j;
+
+               printf("%s: pngcp", pass ? "PASS" : "FAIL");
+
+               for (j=1; j<option_end; ++j)
+                  printf(" %s", argv[j]);
+
+               if (infile != NULL)
+                  printf(" %s", infile);
+
+#              ifdef PNG_PNGCP_TIMING_SUPPORTED
+                  /* When logging output the files for each file, if enabled. */
+                  if ((d.value[OPTIND(&d,time)] & PNGCP_TIME_READ) != 0)
+                     print_time(" read", d.read_time);
+
+                  if ((d.value[OPTIND(&d,time)] & PNGCP_TIME_WRITE) != 0)
+                     print_time(" write", d.write_time);
+#              endif /* PNGCP_TIMING */
+
+               printf("\n");
+               fflush(stdout);
+            }
+         }
+
+         display_clean(&d);
+      }
+      while (i+!(d.options & NOWRITE) < argc);
+         /* I.e. for write cases after the first time through the loop require
+          * there to be at least two arguments left and for the last one to be a
+          * directory (this was checked above).
+          */
+
+      /* Release allocated memory */
+      display_destroy(&d);
+
+#     ifdef PNG_PNGCP_TIMING_SUPPORTED
+         {
+            int output = 0;
+
+            if ((d.value[OPTIND(&d,time)] & PNGCP_TIME_READ) != 0)
+               print_time("read", d.read_time_total), output = 1;
+
+            if ((d.value[OPTIND(&d,time)] & PNGCP_TIME_WRITE) != 0)
+            {
+               if (output) putchar(' ');
+               print_time("write", d.write_time_total);
+               output = 1;
+            }
+
+            if (output) putchar('\n');
+         }
+#     endif /* PNGCP_TIMING */
+
+      return errors != 0;
+   }
+}
+#else /* !READ_PNG || !WRITE_PNG */
+int
+main(void)
+{
+   fprintf(stderr, "pngcp: no support for png_read/write_image\n");
+   return 77;
+}
+#endif /* !READ_PNG || !WRITE_PNG */
diff --git a/contrib/tools/reindent b/contrib/tools/reindent
new file mode 100755
index 0000000..f4df309
--- /dev/null
+++ b/contrib/tools/reindent
@@ -0,0 +1,25 @@
+#!/bin/sh
+
+# reindent a libpng C source
+
+# COPYRIGHT: Written by Glenn Randers-Pehrson, 2016.
+# To the extent possible under law, the author has waived all copyright and
+# related or neighboring rights to this work.  This work is published from:
+# United States.
+
+# Usage:
+# reindent inputtabsize outputtabsize inputcontinuestring outputcontinuestring
+#
+# Assumes that continued lines begin with indentation plus one space, and
+# that continued comments begin with indentation plus " *".
+#
+# eg, to change libpng coding style from 3-space indentation with 4-space
+# continuations to 4-space indentation with 2-space continuations:
+#
+#  reindent 3 4 "\t " "  " < example.c > example.c_4_2
+# and to restore the file back to libpng coding style
+#  reindent 4 3 "  " "    " < example.c_4_2 > example.c_3_4
+
+unexpand --first-only --t $1 | \
+   sed -e "/^	*$3[^\*]/{s/$3/$4/}" | \
+   expand -t $2
diff --git a/example.c b/example.c
index f8591e6..edc8ba2 100644
--- a/example.c
+++ b/example.c
@@ -2,8 +2,8 @@
 #if 0 /* in case someone actually tries to compile this */
 
 /* example.c - an example of using libpng
- * Last changed in libpng 1.6.15 [November 20, 2014]
- * Maintained 1998-2014 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Maintained 1998-2016 Glenn Randers-Pehrson
  * Maintained 1996, 1997 Andreas Dilger)
  * Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  * To the extent possible under law, the authors have waived
@@ -97,7 +97,7 @@
           */
          if (buffer != NULL &&
             png_image_finish_read(&image, NULL/*background*/, buffer,
-               0/*row_stride*/, NULL/*colormap*/) != 0)
+                0/*row_stride*/, NULL/*colormap*/) != 0)
          {
             /* Now write the image out to the second argument.  In the write
              * call 'convert_to_8bit' allows 16-bit data to be squashed down to
@@ -105,7 +105,7 @@
              * to the 8-bit format.
              */
             if (png_image_write_to_file(&image, argv[2], 0/*convert_to_8bit*/,
-               buffer, 0/*row_stride*/, NULL/*colormap*/) != 0)
+                buffer, 0/*row_stride*/, NULL/*colormap*/) != 0)
             {
                /* The image has been written successfully. */
                exit(0);
@@ -295,7 +295,7 @@
     * was compiled with a compatible version of the library.  REQUIRED
     */
    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
-      png_voidp user_error_ptr, user_error_fn, user_warning_fn);
+       png_voidp user_error_ptr, user_error_fn, user_warning_fn);
 
    if (png_ptr == NULL)
    {
@@ -375,7 +375,7 @@
     * low byte.
     */
 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-    png_set_scale_16(png_ptr);
+   png_set_scale_16(png_ptr);
 #else
    png_set_strip_16(png_ptr);
 #endif
@@ -419,10 +419,10 @@
 
    if (png_get_bKGD(png_ptr, info_ptr, &image_background) != 0)
       png_set_background(png_ptr, image_background,
-                         PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
+          PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
    else
       png_set_background(png_ptr, &my_background,
-                         PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
+          PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
 
    /* Some suggestions as to how to get a screen gamma value
     *
@@ -481,7 +481,7 @@
          png_color std_color_cube[MAX_SCREEN_COLORS];
 
          png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
-            MAX_SCREEN_COLORS, NULL, 0);
+             MAX_SCREEN_COLORS, NULL, 0);
       }
       /* This reduces the image to the palette supplied in the file */
       else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette) != 0)
@@ -491,7 +491,7 @@
          png_get_hIST(png_ptr, info_ptr, &histogram);
 
          png_set_quantize(png_ptr, palette, num_palette,
-                        max_screen_colors, histogram, 0);
+             max_screen_colors, histogram, 0);
       }
    }
 #endif /* READ_QUANTIZE */
@@ -530,7 +530,7 @@
     * see the png_read_row() method below:
     */
    number_passes = png_set_interlace_handling(png_ptr);
-#else
+#else /* !READ_INTERLACING */
    number_passes = 1;
 #endif /* READ_INTERLACING */
 
@@ -552,7 +552,7 @@
 
    for (row = 0; row < height; row++)
       row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
-         info_ptr));
+          info_ptr));
 
    /* Now it's time to read the image.  One of these methods is REQUIRED */
 #ifdef entire /* Read the entire image in one go */
@@ -574,10 +574,10 @@
       {
 #ifdef sparkle /* Read the image using the "sparkle" effect. */
          png_read_rows(png_ptr, &row_pointers[y], NULL,
-            number_of_rows);
+             number_of_rows);
 #else no_sparkle /* Read the image using the "rectangle" effect */
          png_read_rows(png_ptr, NULL, &row_pointers[y],
-            number_of_rows);
+             number_of_rows);
 #endif no_sparkle /* Use only one of these two methods */
       }
 
@@ -614,7 +614,7 @@
     * linked libraries.
     */
    *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
-       png_voidp user_error_ptr, user_error_fn, user_warning_fn);
+        png_voidp user_error_ptr, user_error_fn, user_warning_fn);
 
    if (*png_ptr == NULL)
    {
@@ -649,14 +649,14 @@
     * the function png_get_progressive_ptr(png_ptr).
     */
    png_set_progressive_read_fn(*png_ptr, (void *)stream_data,
-      info_callback, row_callback, end_callback);
+       info_callback, row_callback, end_callback);
 
    return (OK);
 }
 
 int
 process_data(png_structp *png_ptr, png_infop *info_ptr,
-   png_bytep buffer, png_uint_32 length)
+    png_bytep buffer, png_uint_32 length)
 {
    if (setjmp(png_jmpbuf((*png_ptr))))
    {
@@ -691,7 +691,7 @@
 }
 
 row_callback(png_structp png_ptr, png_bytep new_row,
-   png_uint_32 row_num, int pass)
+    png_uint_32 row_num, int pass)
 {
    /*
     * This function is called for every row in the image.  If the
@@ -780,7 +780,7 @@
     * in case we are using dynamically linked libraries.  REQUIRED.
     */
    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
-      png_voidp user_error_ptr, user_error_fn, user_warning_fn);
+       png_voidp user_error_ptr, user_error_fn, user_warning_fn);
 
    if (png_ptr == NULL)
    {
@@ -819,7 +819,7 @@
     * png_init_io() here you would call
     */
    png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
-      user_IO_flush_function);
+       user_IO_flush_function);
    /* where user_io_ptr is a structure you want available to the callbacks */
 #endif no_streams /* Only use one initialization method */
 
@@ -842,7 +842,7 @@
     * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED
     */
    png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???,
-      PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+       PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 
    /* Set the palette if there is one.  REQUIRED for indexed-color images */
    palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH
@@ -988,11 +988,11 @@
    png_bytep row_pointers[height];
 
    if (height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
-     png_error (png_ptr, "Image is too tall to process in memory");
+      png_error (png_ptr, "Image is too tall to process in memory");
 
    /* Set up pointers into your "image" byte array */
    for (k = 0; k < height; k++)
-     row_pointers[k] = image + k*width*bytes_per_pixel;
+      row_pointers[k] = image + k*width*bytes_per_pixel;
 
    /* One of the following output methods is REQUIRED */
 
diff --git a/libpng-manual.txt b/libpng-manual.txt
index 541a264..98ac4b1 100644
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -1,6 +1,6 @@
 libpng-manual.txt - A description on how to use and modify libpng
 
- libpng version 1.6.23 - June 9, 2016
+ libpng version 1.6.24 - August 4, 2016
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2016 Glenn Randers-Pehrson
@@ -11,7 +11,7 @@
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.6.23 - June 9, 2016
+ libpng versions 0.97, January 1998, through 1.6.24 - August 4, 2016
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2016 Glenn Randers-Pehrson
 
@@ -559,7 +559,7 @@
 passed in row number, and pass will always be 0.  For the interlaced case the
 same applies unless the row value is 0, in which case the row just handled was
 the last one from one of the preceding passes.  Because interlacing may skip a
-pass you cannot be sure that the preceding pass is just 'pass-1', if you really
+pass you cannot be sure that the preceding pass is just 'pass-1'; if you really
 need to know what the last pass is record (row,pass) from the callback and use
 the last recorded value each time.
 
@@ -2230,7 +2230,8 @@
 after each pass, the "rectangle" effect is generally considered the
 better looking one.
 
-If you only want the "sparkle" effect, just call png_read_rows() as
+If you only want the "sparkle" effect, just call png_read_row() or
+png_read_rows() as
 normal, with the third parameter NULL.  Make sure you make pass over
 the image number_of_passes times, and you don't change the data in the
 rows between calls.  You can change the locations of the data, just
@@ -2239,6 +2240,8 @@
 
     png_read_rows(png_ptr, row_pointers, NULL,
         number_of_rows);
+    or
+    png_read_row(png_ptr, row_pointers, NULL);
 
 If you only want the first effect (the rectangles), do the same as
 before except pass the row buffer in the third parameter, and leave
@@ -2246,6 +2249,8 @@
 
     png_read_rows(png_ptr, NULL, row_pointers,
         number_of_rows);
+    or
+    png_read_row(png_ptr, NULL, row_pointers);
 
 If you don't want libpng to handle the interlacing details, just call
 png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images.
@@ -5345,7 +5350,7 @@
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.6.23 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.24 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.
 
 Libpng only has two year fields.  One is a 2-byte unsigned integer
diff --git a/libpng.3 b/libpng.3
index 86a2945..9162df6 100644
--- a/libpng.3
+++ b/libpng.3
@@ -1,6 +1,6 @@
-.TH LIBPNG 3 "June 9, 2016"
+.TH LIBPNG 3 "August 4, 2016"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.23
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.24
 .SH SYNOPSIS
 \fB
 #include <png.h>\fP
@@ -510,7 +510,7 @@
 .SH LIBPNG.TXT
 libpng-manual.txt - A description on how to use and modify libpng
 
- libpng version 1.6.23 - June 9, 2016
+ libpng version 1.6.24 - August 4, 2016
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2016 Glenn Randers-Pehrson
@@ -521,7 +521,7 @@
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.6.23 - June 9, 2016
+ libpng versions 0.97, January 1998, through 1.6.24 - August 4, 2016
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2016 Glenn Randers-Pehrson
 
@@ -1069,7 +1069,7 @@
 passed in row number, and pass will always be 0.  For the interlaced case the
 same applies unless the row value is 0, in which case the row just handled was
 the last one from one of the preceding passes.  Because interlacing may skip a
-pass you cannot be sure that the preceding pass is just 'pass\-1', if you really
+pass you cannot be sure that the preceding pass is just 'pass\-1'; if you really
 need to know what the last pass is record (row,pass) from the callback and use
 the last recorded value each time.
 
@@ -2740,7 +2740,8 @@
 after each pass, the "rectangle" effect is generally considered the
 better looking one.
 
-If you only want the "sparkle" effect, just call png_read_rows() as
+If you only want the "sparkle" effect, just call png_read_row() or
+png_read_rows() as
 normal, with the third parameter NULL.  Make sure you make pass over
 the image number_of_passes times, and you don't change the data in the
 rows between calls.  You can change the locations of the data, just
@@ -2749,6 +2750,8 @@
 
     png_read_rows(png_ptr, row_pointers, NULL,
         number_of_rows);
+    or
+    png_read_row(png_ptr, row_pointers, NULL);
 
 If you only want the first effect (the rectangles), do the same as
 before except pass the row buffer in the third parameter, and leave
@@ -2756,6 +2759,8 @@
 
     png_read_rows(png_ptr, NULL, row_pointers,
         number_of_rows);
+    or
+    png_read_row(png_ptr, NULL, row_pointers);
 
 If you don't want libpng to handle the interlacing details, just call
 png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images.
@@ -5855,7 +5860,7 @@
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.6.23 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.24 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.
 
 Libpng only has two year fields.  One is a 2-byte unsigned integer
@@ -5957,7 +5962,7 @@
  ...
  1.5.27                  15    10527  15.so.15.27[.0]
  ...
- 1.6.23                  16    10623  16.so.16.23[.0]
+ 1.6.24                  16    10624  16.so.16.24[.0]
 
 Henceforth the source version will match the shared-library minor
 and patch numbers; the shared-library major version number will be
@@ -6013,7 +6018,7 @@
 
 Thanks to Frank J. T. Wojcik for helping with the documentation.
 
-Libpng version 1.6.23 - June 9, 2016:
+Libpng version 1.6.24 - August 4, 2016:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
 
@@ -6038,7 +6043,7 @@
 
 This code is released under the libpng license.
 
-libpng versions 1.0.7, July 1, 2000 through 1.6.23, June 9, 2016 are
+libpng versions 1.0.7, July 1, 2000 through 1.6.24, August 4, 2016 are
 Copyright (c) 2000-2002, 2004, 2006-2016 Glenn Randers-Pehrson, are
 derived from libpng-1.0.6, and are distributed according to the same
 disclaimer and license as libpng-1.0.6 with the following individuals
@@ -6163,7 +6168,7 @@
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-June 9, 2016
+August 4, 2016
 
 .\" end of man page
 
diff --git a/libpngpf.3 b/libpngpf.3
index ea1a465..4e8e6ed 100644
--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,6 +1,6 @@
-.TH LIBPNGPF 3 "June 9, 2016"
+.TH LIBPNGPF 3 "August 4, 2016"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.23
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.24
 (private functions)
 .SH SYNOPSIS
 \fB#include \fI"pngpriv.h"
diff --git a/png.5 b/png.5
index 8ff1639..0df6f9a 100644
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "June 9, 2016"
+.TH PNG 5 "August 4, 2016"
 .SH NAME
 png \- Portable Network Graphics (PNG) format
 .SH DESCRIPTION
diff --git a/png.c b/png.c
index 1720ca0..0843ebb 100644
--- a/png.c
+++ b/png.c
@@ -1,7 +1,7 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * Last changed in libpng 1.6.19 [November 12, 2015]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -14,7 +14,7 @@
 #include "pngpriv.h"
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_23 Your_png_h_is_not_version_1_6_23;
+typedef png_libpng_version_1_6_24 Your_png_h_is_not_version_1_6_24;
 
 /* Tells libpng that we have already handled the first "num_bytes" bytes
  * of the PNG file signature.  If the PNG data is embedded into another
@@ -85,7 +85,7 @@
    if (items >= (~(png_alloc_size_t)0)/size)
    {
       png_warning (png_voidcast(png_structrp, png_ptr),
-         "Potential overflow in png_zalloc()");
+          "Potential overflow in png_zalloc()");
       return NULL;
    }
 
@@ -172,10 +172,10 @@
 int
 png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)
 {
-     /* Libpng versions 1.0.0 and later are binary compatible if the version
-      * string matches through the second '.'; we must recompile any
-      * applications that use any older library version.
-      */
+   /* Libpng versions 1.0.0 and later are binary compatible if the version
+    * string matches through the second '.'; we must recompile any
+    * applications that use any older library version.
+    */
 
    if (user_png_ver != NULL)
    {
@@ -297,7 +297,7 @@
          if (png_user_version_check(&create_struct, user_png_ver) != 0)
          {
             png_structrp png_ptr = png_voidcast(png_structrp,
-               png_malloc_warn(&create_struct, (sizeof *png_ptr)));
+                png_malloc_warn(&create_struct, (sizeof *png_ptr)));
 
             if (png_ptr != NULL)
             {
@@ -346,7 +346,7 @@
     * has always been done in 'example.c'.
     */
    info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,
-      (sizeof *info_ptr)));
+       (sizeof *info_ptr)));
 
    if (info_ptr != NULL)
       memset(info_ptr, 0, (sizeof *info_ptr));
@@ -402,7 +402,7 @@
  */
 PNG_FUNCTION(void,PNGAPI
 png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size),
-   PNG_DEPRECATED)
+    PNG_DEPRECATED)
 {
    png_inforp info_ptr = *ptr_ptr;
 
@@ -417,7 +417,7 @@
       /* The following line is why this API should not be used: */
       free(info_ptr);
       info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
-         (sizeof *info_ptr)));
+          (sizeof *info_ptr)));
       if (info_ptr == NULL)
          return;
       *ptr_ptr = info_ptr;
@@ -430,7 +430,7 @@
 /* The following API is not called internally */
 void PNGAPI
 png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,
-   int freer, png_uint_32 mask)
+    int freer, png_uint_32 mask)
 {
    png_debug(1, "in png_data_freer");
 
@@ -449,7 +449,7 @@
 
 void PNGAPI
 png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask,
-   int num)
+    int num)
 {
    png_debug(1, "in png_free_data");
 
@@ -775,14 +775,14 @@
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-      "libpng version 1.6.23 - June 9, 2016" PNG_STRING_NEWLINE \
+      "libpng version 1.6.24 - August 4, 2016" PNG_STRING_NEWLINE \
       "Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson" \
       PNG_STRING_NEWLINE \
       "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
       "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
       PNG_STRING_NEWLINE;
 #  else
-   return "libpng version 1.6.23 - June 9, 2016\
+   return "libpng version 1.6.24 - August 4, 2016\
       Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -1033,7 +1033,7 @@
 #ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */
 static int
 png_colorspace_check_gamma(png_const_structrp png_ptr,
-   png_colorspacerp colorspace, png_fixed_point gAMA, int from)
+    png_colorspacerp colorspace, png_fixed_point gAMA, int from)
    /* This is called to check a new gamma value against an existing one.  The
     * routine returns false if the new gamma value should not be written.
     *
@@ -1047,7 +1047,7 @@
    png_fixed_point gtest;
 
    if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
-      (png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) == 0  ||
+       (png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) == 0  ||
       png_gamma_significant(gtest) != 0))
    {
       /* Either this is an sRGB image, in which case the calculated gamma
@@ -1059,7 +1059,7 @@
       if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2)
       {
          png_chunk_report(png_ptr, "gamma value does not match sRGB",
-            PNG_CHUNK_ERROR);
+             PNG_CHUNK_ERROR);
          /* Do not overwrite an sRGB value */
          return from == 2;
       }
@@ -1067,7 +1067,7 @@
       else /* sRGB tag not involved */
       {
          png_chunk_report(png_ptr, "gamma value does not match libpng estimate",
-            PNG_CHUNK_WARNING);
+             PNG_CHUNK_WARNING);
          return from == 1;
       }
    }
@@ -1077,7 +1077,7 @@
 
 void /* PRIVATE */
 png_colorspace_set_gamma(png_const_structrp png_ptr,
-   png_colorspacerp colorspace, png_fixed_point gAMA)
+    png_colorspacerp colorspace, png_fixed_point gAMA)
 {
    /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
     * occur.  Since the fixed point representation is asymetrical it is
@@ -1635,8 +1635,8 @@
 
 static int
 png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr,
-   png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,
-   int preferred)
+    png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,
+    int preferred)
 {
    if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
       return 0;
@@ -1683,7 +1683,7 @@
 
 int /* PRIVATE */
 png_colorspace_set_chromaticities(png_const_structrp png_ptr,
-   png_colorspacerp colorspace, const png_xy *xy, int preferred)
+    png_colorspacerp colorspace, const png_xy *xy, int preferred)
 {
    /* We must check the end points to ensure they are reasonable - in the past
     * color management systems have crashed as a result of getting bogus
@@ -1697,7 +1697,7 @@
    {
       case 0: /* success */
          return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ,
-            preferred);
+             preferred);
 
       case 1:
          /* We can't invert the chromaticities so we can't produce value XYZ
@@ -1720,7 +1720,7 @@
 
 int /* PRIVATE */
 png_colorspace_set_endpoints(png_const_structrp png_ptr,
-   png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)
+    png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)
 {
    png_XYZ XYZ = *XYZ_in;
    png_xy xy;
@@ -1729,7 +1729,7 @@
    {
       case 0:
          return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ,
-            preferred);
+             preferred);
 
       case 1:
          /* End points are invalid. */
@@ -1786,7 +1786,7 @@
 
 static int
 png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace,
-   png_const_charp name, png_alloc_size_t value, png_const_charp reason)
+    png_const_charp name, png_alloc_size_t value, png_const_charp reason)
 {
    size_t pos;
    char message[196]; /* see below for calculation */
@@ -1811,8 +1811,8 @@
          char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/
 
          pos = png_safecat(message, (sizeof message), pos,
-            png_format_number(number, number+(sizeof number),
-               PNG_NUMBER_FORMAT_x, value));
+             png_format_number(number, number+(sizeof number),
+             PNG_NUMBER_FORMAT_x, value));
          pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/
       }
 #  endif
@@ -1826,7 +1826,7 @@
     * application errors the PNG won't be written.)
     */
    png_chunk_report(png_ptr, message,
-      (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);
+       (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);
 
    return 0;
 }
@@ -1835,7 +1835,7 @@
 #ifdef PNG_sRGB_SUPPORTED
 int /* PRIVATE */
 png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,
-   int intent)
+    int intent)
 {
    /* sRGB sets known gamma, end points and (from the chunk) intent. */
    /* IMPORTANT: these are not necessarily the values found in an ICC profile
@@ -1872,10 +1872,10 @@
     */
    if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)
       return png_icc_profile_error(png_ptr, colorspace, "sRGB",
-         (unsigned)intent, "invalid sRGB rendering intent");
+          (unsigned)intent, "invalid sRGB rendering intent");
 
    if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&
-      colorspace->rendering_intent != intent)
+       colorspace->rendering_intent != intent)
       return png_icc_profile_error(png_ptr, colorspace, "sRGB",
          (unsigned)intent, "inconsistent rendering intents");
 
@@ -1889,8 +1889,8 @@
     * warn but overwrite the value with the correct one.
     */
    if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 &&
-      !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,
-         100))
+       !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,
+       100))
       png_chunk_report(png_ptr, "cHRM chunk does not match sRGB",
          PNG_CHUNK_ERROR);
 
@@ -1898,7 +1898,7 @@
     * returns true when the 'from' argument corresponds to sRGB (2).
     */
    (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE,
-      2/*from sRGB*/);
+       2/*from sRGB*/);
 
    /* intent: bugs in GCC force 'int' to be used as the parameter type. */
    colorspace->rendering_intent = (png_uint_16)intent;
@@ -1933,19 +1933,19 @@
 
 int /* PRIVATE */
 png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,
-   png_const_charp name, png_uint_32 profile_length)
+    png_const_charp name, png_uint_32 profile_length)
 {
    if (profile_length < 132)
       return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
-         "too short");
+          "too short");
 
    return 1;
 }
 
 int /* PRIVATE */
 png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
-   png_const_charp name, png_uint_32 profile_length,
-   png_const_bytep profile/* first 132 bytes only */, int color_type)
+    png_const_charp name, png_uint_32 profile_length,
+    png_const_bytep profile/* first 132 bytes only */, int color_type)
 {
    png_uint_32 temp;
 
@@ -1957,18 +1957,18 @@
    temp = png_get_uint_32(profile);
    if (temp != profile_length)
       return png_icc_profile_error(png_ptr, colorspace, name, temp,
-         "length does not match profile");
+          "length does not match profile");
 
    temp = (png_uint_32) (*(profile+8));
    if (temp > 3 && (profile_length & 3))
       return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
-         "invalid length");
+          "invalid length");
 
    temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */
    if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */
       profile_length < 132+12*temp) /* truncated tag table */
       return png_icc_profile_error(png_ptr, colorspace, name, temp,
-         "tag count too large");
+          "tag count too large");
 
    /* The 'intent' must be valid or we can't store it, ICC limits the intent to
     * 16 bits.
@@ -1976,14 +1976,14 @@
    temp = png_get_uint_32(profile+64);
    if (temp >= 0xffff) /* The ICC limit */
       return png_icc_profile_error(png_ptr, colorspace, name, temp,
-         "invalid rendering intent");
+          "invalid rendering intent");
 
    /* This is just a warning because the profile may be valid in future
     * versions.
     */
    if (temp >= PNG_sRGB_INTENT_LAST)
       (void)png_icc_profile_error(png_ptr, NULL, name, temp,
-         "intent outside defined range");
+          "intent outside defined range");
 
    /* At this point the tag table can't be checked because it hasn't necessarily
     * been loaded; however, various header fields can be checked.  These checks
@@ -2000,7 +2000,7 @@
    temp = png_get_uint_32(profile+36); /* signature 'ascp' */
    if (temp != 0x61637370)
       return png_icc_profile_error(png_ptr, colorspace, name, temp,
-         "invalid signature");
+          "invalid signature");
 
    /* Currently the PCS illuminant/adopted white point (the computational
     * white point) are required to be D50,
@@ -2011,7 +2011,7 @@
     */
    if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0)
       (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/,
-         "PCS illuminant is not D50");
+          "PCS illuminant is not D50");
 
    /* The PNG spec requires this:
     * "If the iCCP chunk is present, the image samples conform to the colour
@@ -2039,18 +2039,18 @@
       case 0x52474220: /* 'RGB ' */
          if ((color_type & PNG_COLOR_MASK_COLOR) == 0)
             return png_icc_profile_error(png_ptr, colorspace, name, temp,
-               "RGB color space not permitted on grayscale PNG");
+                "RGB color space not permitted on grayscale PNG");
          break;
 
       case 0x47524159: /* 'GRAY' */
          if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
             return png_icc_profile_error(png_ptr, colorspace, name, temp,
-               "Gray color space not permitted on RGB PNG");
+                "Gray color space not permitted on RGB PNG");
          break;
 
       default:
          return png_icc_profile_error(png_ptr, colorspace, name, temp,
-            "invalid ICC profile color space");
+             "invalid ICC profile color space");
    }
 
    /* It is up to the application to check that the profile class matches the
@@ -2075,7 +2075,7 @@
       case 0x61627374: /* 'abst' */
          /* May not be embedded in an image */
          return png_icc_profile_error(png_ptr, colorspace, name, temp,
-            "invalid embedded Abstract ICC profile");
+             "invalid embedded Abstract ICC profile");
 
       case 0x6c696e6b: /* 'link' */
          /* DeviceLink profiles cannot be interpreted in a non-device specific
@@ -2085,7 +2085,7 @@
           * PNG.
           */
          return png_icc_profile_error(png_ptr, colorspace, name, temp,
-            "unexpected DeviceLink ICC profile class");
+             "unexpected DeviceLink ICC profile class");
 
       case 0x6e6d636c: /* 'nmcl' */
          /* A NamedColor profile is also device specific, however it doesn't
@@ -2093,7 +2093,7 @@
           * certainly it will fail the tests below.
           */
          (void)png_icc_profile_error(png_ptr, NULL, name, temp,
-            "unexpected NamedColor ICC profile class");
+             "unexpected NamedColor ICC profile class");
          break;
 
       default:
@@ -2103,7 +2103,7 @@
           * understood profiles.
           */
          (void)png_icc_profile_error(png_ptr, NULL, name, temp,
-            "unrecognized ICC profile class");
+             "unrecognized ICC profile class");
          break;
    }
 
@@ -2119,7 +2119,7 @@
 
       default:
          return png_icc_profile_error(png_ptr, colorspace, name, temp,
-            "unexpected ICC PCS encoding");
+             "unexpected ICC PCS encoding");
    }
 
    return 1;
@@ -2127,8 +2127,8 @@
 
 int /* PRIVATE */
 png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,
-   png_const_charp name, png_uint_32 profile_length,
-   png_const_bytep profile /* header plus whole tag table */)
+    png_const_charp name, png_uint_32 profile_length,
+    png_const_bytep profile /* header plus whole tag table */)
 {
    png_uint_32 tag_count = png_get_uint_32(profile+128);
    png_uint_32 itag;
@@ -2156,7 +2156,7 @@
           * alignment.
           */
          (void)png_icc_profile_error(png_ptr, NULL, name, tag_id,
-            "ICC profile tag start not a multiple of 4");
+             "ICC profile tag start not a multiple of 4");
       }
 
       /* This is a hard error; potentially it can cause read outside the
@@ -2164,7 +2164,7 @@
        */
       if (tag_start > profile_length || tag_length > profile_length - tag_start)
          return png_icc_profile_error(png_ptr, colorspace, name, tag_id,
-            "ICC profile tag outside profile");
+             "ICC profile tag outside profile");
    }
 
    return 1; /* success, maybe with warnings */
@@ -2192,22 +2192,22 @@
     */
    /* adler32, crc32, MD5[4], intent, date, length, file-name */
    PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,
-      PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,
-      "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")
+       PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,
+       "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")
 
    /* ICC sRGB v2 perceptual no black-compensation: */
    PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,
-      PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,
-      "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")
+       PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,
+       "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")
 
    PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,
-      PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,
-      "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")
+       PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,
+       "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")
 
    /* ICC sRGB v4 perceptual */
    PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,
-      PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,
-      "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")
+       PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,
+       "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")
 
    /* The following profiles have no known MD5 checksum. If there is a match
     * on the (empty) MD5 the other fields are used to attempt a match and
@@ -2215,8 +2215,8 @@
     * which suggests that they were also made by Hewlett Packard.
     */
    PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,
-      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,
-      "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")
+       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,
+       "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")
 
    /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not
     * match the D50 PCS illuminant in the header (it is in fact the D65 values,
@@ -2226,17 +2226,17 @@
     * chromaticAdaptationTag.
     */
    PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,
-      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,
-      "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")
+       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,
+       "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")
 
    PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,
-      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,
-      "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")
+       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,
+       "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")
 };
 
 static int
 png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,
-   png_const_bytep profile, uLong adler)
+    png_const_bytep profile, uLong adler)
 {
    /* The quick check is to verify just the MD5 signature and trust the
     * rest of the data.  Because the profile has already been verified for
@@ -2320,7 +2320,7 @@
                       * which is made irrelevant by this error.
                       */
                      png_chunk_report(png_ptr, "known incorrect sRGB profile",
-                        PNG_CHUNK_ERROR);
+                         PNG_CHUNK_ERROR);
                   }
 
                   /* Warn that this being done; this isn't even an error since
@@ -2330,8 +2330,8 @@
                   else if (png_sRGB_checks[i].have_md5 == 0)
                   {
                      png_chunk_report(png_ptr,
-                        "out-of-date sRGB profile with no signature",
-                        PNG_CHUNK_WARNING);
+                         "out-of-date sRGB profile with no signature",
+                         PNG_CHUNK_WARNING);
                   }
 
                   return 1+png_sRGB_checks[i].is_broken;
@@ -2354,38 +2354,36 @@
 
    return 0; /* no match */
 }
-#endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */
 
 void /* PRIVATE */
 png_icc_set_sRGB(png_const_structrp png_ptr,
-   png_colorspacerp colorspace, png_const_bytep profile, uLong adler)
+    png_colorspacerp colorspace, png_const_bytep profile, uLong adler)
 {
    /* Is this profile one of the known ICC sRGB profiles?  If it is, just set
     * the sRGB information.
     */
-#if PNG_sRGB_PROFILE_CHECKS >= 0
    if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler) != 0)
-#endif
       (void)png_colorspace_set_sRGB(png_ptr, colorspace,
          (int)/*already checked*/png_get_uint_32(profile+64));
 }
+#endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */
 #endif /* sRGB */
 
 int /* PRIVATE */
 png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace,
-   png_const_charp name, png_uint_32 profile_length, png_const_bytep profile,
-   int color_type)
+    png_const_charp name, png_uint_32 profile_length, png_const_bytep profile,
+    int color_type)
 {
    if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
       return 0;
 
    if (png_icc_check_length(png_ptr, colorspace, name, profile_length) != 0 &&
        png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,
-          color_type) != 0 &&
+           color_type) != 0 &&
        png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
-          profile) != 0)
+           profile) != 0)
    {
-#     ifdef PNG_sRGB_SUPPORTED
+#     if defined(PNG_sRGB_SUPPORTED) && PNG_sRGB_PROFILE_CHECKS >= 0
          /* If no sRGB support, don't try storing sRGB information */
          png_icc_set_sRGB(png_ptr, colorspace, profile, 0);
 #     endif
@@ -2444,7 +2442,7 @@
          /* Check for an internal error. */
          if (r+g+b != 32768)
             png_error(png_ptr,
-               "internal error handling cHRM coefficients");
+                "internal error handling cHRM coefficients");
 
          else
          {
@@ -2470,7 +2468,7 @@
 static int /* PRIVATE */
 png_gt(size_t a, size_t b)
 {
-    return a > b;
+   return a > b;
 }
 #else
 #   define png_gt(a,b) ((a) > (b))
@@ -2478,9 +2476,9 @@
 
 void /* PRIVATE */
 png_check_IHDR(png_const_structrp png_ptr,
-   png_uint_32 width, png_uint_32 height, int bit_depth,
-   int color_type, int interlace_type, int compression_type,
-   int filter_type)
+    png_uint_32 width, png_uint_32 height, int bit_depth,
+    int color_type, int interlace_type, int compression_type,
+    int filter_type)
 {
    int error = 0;
 
@@ -2643,7 +2641,7 @@
 
 int /* PRIVATE */
 png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
-   png_size_tp whereami)
+    png_size_tp whereami)
 {
    int state = *statep;
    png_size_t i = *whereami;
@@ -3806,25 +3804,25 @@
 {
    if (value > 0 && value < 65535)
    {
-#     ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
-         /* The same (unsigned int)->(double) constraints apply here as above,
-          * however in this case the (unsigned int) to (int) conversion can
-          * overflow on an ANSI-C90 compliant system so the cast needs to ensure
-          * that this is not possible.
-          */
-         double r = floor(65535*pow((png_int_32)value/65535.,
-                     gamma_val*.00001)+.5);
-         return (png_uint_16)r;
-#     else
-         png_int_32 lg2 = png_log16bit(value);
-         png_fixed_point res;
+# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
+      /* The same (unsigned int)->(double) constraints apply here as above,
+       * however in this case the (unsigned int) to (int) conversion can
+       * overflow on an ANSI-C90 compliant system so the cast needs to ensure
+       * that this is not possible.
+       */
+      double r = floor(65535*pow((png_int_32)value/65535.,
+          gamma_val*.00001)+.5);
+      return (png_uint_16)r;
+# else
+      png_int_32 lg2 = png_log16bit(value);
+      png_fixed_point res;
 
-         if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0)
-            return png_exp16bit(res);
+      if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0)
+         return png_exp16bit(res);
 
-         /* Overflow. */
-         value = 0;
-#     endif
+      /* Overflow. */
+      value = 0;
+# endif
    }
 
    return (png_uint_16)value;
@@ -3863,7 +3861,7 @@
  */
 static void
 png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,
-   PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
+    PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
 {
    /* Various values derived from 'shift': */
    PNG_CONST unsigned int num = 1U << (8U - shift);
@@ -3940,7 +3938,7 @@
  */
 static void
 png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,
-   PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
+    PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
 {
    PNG_CONST unsigned int num = 1U << (8U - shift);
    PNG_CONST unsigned int max = (1U << (16U - shift))-1U;
@@ -4008,7 +4006,7 @@
  */
 static void
 png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,
-   PNG_CONST png_fixed_point gamma_val)
+    PNG_CONST png_fixed_point gamma_val)
 {
    unsigned int i;
    png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256);
@@ -4088,131 +4086,133 @@
 void /* PRIVATE */
 png_build_gamma_table(png_structrp png_ptr, int bit_depth)
 {
-  png_debug(1, "in png_build_gamma_table");
+   png_debug(1, "in png_build_gamma_table");
 
-  /* Remove any existing table; this copes with multiple calls to
-   * png_read_update_info.  The warning is because building the gamma tables
-   * multiple times is a performance hit - it's harmless but the ability to call
-   * png_read_update_info() multiple times is new in 1.5.6 so it seems sensible
-   * to warn if the app introduces such a hit.
-   */
-  if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL)
-  {
-    png_warning(png_ptr, "gamma table being rebuilt");
-    png_destroy_gamma_table(png_ptr);
-  }
+   /* Remove any existing table; this copes with multiple calls to
+    * png_read_update_info. The warning is because building the gamma tables
+    * multiple times is a performance hit - it's harmless but the ability to
+    * call png_read_update_info() multiple times is new in 1.5.6 so it seems
+    * sensible to warn if the app introduces such a hit.
+    */
+   if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL)
+   {
+      png_warning(png_ptr, "gamma table being rebuilt");
+      png_destroy_gamma_table(png_ptr);
+   }
 
-  if (bit_depth <= 8)
-  {
-     png_build_8bit_table(png_ptr, &png_ptr->gamma_table,
-         png_ptr->screen_gamma > 0 ?  png_reciprocal2(png_ptr->colorspace.gamma,
-         png_ptr->screen_gamma) : PNG_FP_1);
+   if (bit_depth <= 8)
+   {
+      png_build_8bit_table(png_ptr, &png_ptr->gamma_table,
+          png_ptr->screen_gamma > 0 ?
+          png_reciprocal2(png_ptr->colorspace.gamma,
+          png_ptr->screen_gamma) : PNG_FP_1);
 
 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
    defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
    defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
-     if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0)
-     {
-        png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1,
-            png_reciprocal(png_ptr->colorspace.gamma));
+      if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0)
+      {
+         png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1,
+             png_reciprocal(png_ptr->colorspace.gamma));
 
-        png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1,
-            png_ptr->screen_gamma > 0 ?  png_reciprocal(png_ptr->screen_gamma) :
-            png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
-     }
+         png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1,
+             png_ptr->screen_gamma > 0 ?
+             png_reciprocal(png_ptr->screen_gamma) :
+             png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
+      }
 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
-  }
+   }
 #ifdef PNG_16BIT_SUPPORTED
-  else
-  {
-     png_byte shift, sig_bit;
+   else
+   {
+      png_byte shift, sig_bit;
 
-     if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
-     {
-        sig_bit = png_ptr->sig_bit.red;
+      if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
+      {
+         sig_bit = png_ptr->sig_bit.red;
 
-        if (png_ptr->sig_bit.green > sig_bit)
-           sig_bit = png_ptr->sig_bit.green;
+         if (png_ptr->sig_bit.green > sig_bit)
+            sig_bit = png_ptr->sig_bit.green;
 
-        if (png_ptr->sig_bit.blue > sig_bit)
-           sig_bit = png_ptr->sig_bit.blue;
-     }
-     else
-        sig_bit = png_ptr->sig_bit.gray;
+         if (png_ptr->sig_bit.blue > sig_bit)
+            sig_bit = png_ptr->sig_bit.blue;
+      }
+      else
+         sig_bit = png_ptr->sig_bit.gray;
 
-     /* 16-bit gamma code uses this equation:
-      *
-      *   ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]
-      *
-      * Where 'iv' is the input color value and 'ov' is the output value -
-      * pow(iv, gamma).
-      *
-      * Thus the gamma table consists of up to 256 256-entry tables.  The table
-      * is selected by the (8-gamma_shift) most significant of the low 8 bits of
-      * the color value then indexed by the upper 8 bits:
-      *
-      *   table[low bits][high 8 bits]
-      *
-      * So the table 'n' corresponds to all those 'iv' of:
-      *
-      *   <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>
-      *
-      */
-     if (sig_bit > 0 && sig_bit < 16U)
-        /* shift == insignificant bits */
-        shift = (png_byte)((16U - sig_bit) & 0xff);
+      /* 16-bit gamma code uses this equation:
+       *
+       *   ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]
+       *
+       * Where 'iv' is the input color value and 'ov' is the output value -
+       * pow(iv, gamma).
+       *
+       * Thus the gamma table consists of up to 256 256-entry tables.  The table
+       * is selected by the (8-gamma_shift) most significant of the low 8 bits
+       * of the color value then indexed by the upper 8 bits:
+       *
+       *   table[low bits][high 8 bits]
+       *
+       * So the table 'n' corresponds to all those 'iv' of:
+       *
+       *   <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>
+       *
+       */
+      if (sig_bit > 0 && sig_bit < 16U)
+         /* shift == insignificant bits */
+         shift = (png_byte)((16U - sig_bit) & 0xff);
 
-     else
-        shift = 0; /* keep all 16 bits */
+      else
+         shift = 0; /* keep all 16 bits */
 
-     if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
-     {
-        /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
-         * the significant bits in the *input* when the output will
-         * eventually be 8 bits.  By default it is 11.
-         */
-        if (shift < (16U - PNG_MAX_GAMMA_8))
-           shift = (16U - PNG_MAX_GAMMA_8);
-     }
+      if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
+      {
+         /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
+          * the significant bits in the *input* when the output will
+          * eventually be 8 bits.  By default it is 11.
+          */
+         if (shift < (16U - PNG_MAX_GAMMA_8))
+            shift = (16U - PNG_MAX_GAMMA_8);
+      }
 
-     if (shift > 8U)
-        shift = 8U; /* Guarantees at least one table! */
+      if (shift > 8U)
+         shift = 8U; /* Guarantees at least one table! */
 
-     png_ptr->gamma_shift = shift;
+      png_ptr->gamma_shift = shift;
 
-     /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
-      * PNG_COMPOSE).  This effectively smashed the background calculation for
-      * 16-bit output because the 8-bit table assumes the result will be reduced
-      * to 8 bits.
-      */
-     if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
-         png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
-         png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,
-         png_ptr->screen_gamma) : PNG_FP_1);
+      /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
+       * PNG_COMPOSE).  This effectively smashed the background calculation for
+       * 16-bit output because the 8-bit table assumes the result will be
+       * reduced to 8 bits.
+       */
+      if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
+          png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
+          png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,
+          png_ptr->screen_gamma) : PNG_FP_1);
 
-     else
-         png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,
-         png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma,
-         png_ptr->screen_gamma) : PNG_FP_1);
+      else
+          png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,
+          png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma,
+          png_ptr->screen_gamma) : PNG_FP_1);
 
 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
    defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
    defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
-     if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0)
-     {
-        png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift,
-            png_reciprocal(png_ptr->colorspace.gamma));
+      if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0)
+      {
+         png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift,
+             png_reciprocal(png_ptr->colorspace.gamma));
 
-        /* Notice that the '16 from 1' table should be full precision, however
-         * the lookup on this table still uses gamma_shift, so it can't be.
-         * TODO: fix this.
-         */
-        png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift,
-            png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) :
-            png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
-     }
+         /* Notice that the '16 from 1' table should be full precision, however
+          * the lookup on this table still uses gamma_shift, so it can't be.
+          * TODO: fix this.
+          */
+         png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift,
+             png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) :
+             png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
+      }
 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
-  }
+   }
 #endif /* 16BIT */
 }
 #endif /* READ_GAMMA */
diff --git a/png.h b/png.h
index 1efb0b0..ebfb3dd 100644
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.6.23, June 9, 2016
+ * libpng version 1.6.24, August 4, 2016
  *
  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -12,7 +12,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.6.23, June 9, 2016:
+ *   libpng versions 0.97, January 1998, through 1.6.24, August 4, 2016:
  *     Glenn Randers-Pehrson.
  *   See also "Contributing Authors", below.
  */
@@ -29,7 +29,7 @@
  * files that are distributed with libpng have other copyright owners and
  * are released under other open source licenses.
  *
- * libpng versions 1.0.7, July 1, 2000 through 1.6.23, June 9, 2016 are
+ * libpng versions 1.0.7, July 1, 2000 through 1.6.24, August 4, 2016 are
  * Copyright (c) 2000-2002, 2004, 2006-2016 Glenn Randers-Pehrson, are
  * derived from libpng-1.0.6, and are distributed according to the same
  * disclaimer and license as libpng-1.0.6 with the following individuals
@@ -217,7 +217,7 @@
  *    ...
  *    1.5.27                  15    10527  15.so.15.27[.0]
  *    ...
- *    1.6.23                  16    10623  16.so.16.23[.0]
+ *    1.6.24                  16    10624  16.so.16.24[.0]
  *
  *    Henceforth the source version will match the shared-library major
  *    and minor numbers; the shared-library major version number will be
@@ -245,13 +245,13 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    June 9, 2016
+ *    August 4, 2016
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
  *
  *    This is your unofficial assurance that libpng from version 0.71 and
- *    upward through 1.6.23 are Y2K compliant.  It is my belief that
+ *    upward through 1.6.24 are Y2K compliant.  It is my belief that
  *    earlier versions were also Y2K compliant.
  *
  *    Libpng only has two year fields.  One is a 2-byte unsigned integer
@@ -313,9 +313,8 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.6.23"
-#define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.6.23 - June 9, 2016\n"
+#define PNG_LIBPNG_VER_STRING "1.6.24"
+#define PNG_HEADER_VERSION_STRING " libpng version 1.6.24 - August 4, 2016\n"
 
 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -323,7 +322,7 @@
 /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
 #define PNG_LIBPNG_VER_MAJOR   1
 #define PNG_LIBPNG_VER_MINOR   6
-#define PNG_LIBPNG_VER_RELEASE 23
+#define PNG_LIBPNG_VER_RELEASE 24
 
 /* This should match the numeric part of the final component of
  * PNG_LIBPNG_VER_STRING, omitting any leading zero:
@@ -354,20 +353,20 @@
  * version 1.0.0 was mis-numbered 100 instead of 10000).  From
  * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release
  */
-#define PNG_LIBPNG_VER 10623 /* 1.6.23 */
+#define PNG_LIBPNG_VER 10624 /* 1.6.24 */
 
 /* Library configuration: these options cannot be changed after
  * the library has been built.
  */
 #ifndef PNGLCONF_H
-    /* If pnglibconf.h is missing, you can
-     * copy scripts/pnglibconf.h.prebuilt to pnglibconf.h
-     */
+/* If pnglibconf.h is missing, you can
+ * copy scripts/pnglibconf.h.prebuilt to pnglibconf.h
+ */
 #   include "pnglibconf.h"
 #endif
 
 #ifndef PNG_VERSION_INFO_ONLY
-   /* Machine specific configuration. */
+/* Machine specific configuration. */
 #  include "pngconf.h"
 #endif
 
@@ -464,7 +463,7 @@
 /* This triggers a compiler error in png.c, if png.c and png.h
  * do not agree upon the version number.
  */
-typedef char* png_libpng_version_1_6_23;
+typedef char* png_libpng_version_1_6_24;
 
 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
  *
@@ -657,17 +656,17 @@
  */
 typedef struct png_unknown_chunk_t
 {
-    png_byte name[5]; /* Textual chunk name with '\0' terminator */
-    png_byte *data;   /* Data, should not be modified on read! */
-    png_size_t size;
+   png_byte name[5]; /* Textual chunk name with '\0' terminator */
+   png_byte *data;   /* Data, should not be modified on read! */
+   png_size_t size;
 
-    /* On write 'location' must be set using the flag values listed below.
-     * Notice that on read it is set by libpng however the values stored have
-     * more bits set than are listed below.  Always treat the value as a
-     * bitmask.  On write set only one bit - setting multiple bits may cause the
-     * chunk to be written in multiple places.
-     */
-    png_byte location; /* mode of operation at read time */
+   /* On write 'location' must be set using the flag values listed below.
+    * Notice that on read it is set by libpng however the values stored have
+    * more bits set than are listed below.  Always treat the value as a
+    * bitmask.  On write set only one bit - setting multiple bits may cause the
+    * chunk to be written in multiple places.
+    */
+   png_byte location; /* mode of operation at read time */
 }
 png_unknown_chunk;
 
@@ -2300,8 +2299,10 @@
  *    except for the IHDR, PLTE, tRNS, IDAT, and IEND chunks (which continue to
  *    be processed by libpng.
  */
+#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 PNG_EXPORT(172, void, png_set_keep_unknown_chunks, (png_structrp png_ptr,
     int keep, png_const_bytep chunk_list, int num_chunks));
+#endif /* HANDLE_AS_UNKNOWN */
 
 /* The "keep" PNG_HANDLE_CHUNK_ parameter for the specified chunk is returned;
  * the result is therefore true (non-zero) if special handling is required,
@@ -2309,7 +2310,7 @@
  */
 PNG_EXPORT(173, int, png_handle_as_unknown, (png_const_structrp png_ptr,
     png_const_bytep chunk_name));
-#endif
+#endif /* SET_UNKNOWN_CHUNKS */
 
 #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
 PNG_EXPORT(174, void, png_set_unknown_chunks, (png_const_structrp png_ptr,
@@ -2530,33 +2531,37 @@
 
  /* fg and bg should be in `gamma 1.0' space; alpha is the opacity */
 
-#  define png_composite(composite, fg, alpha, bg)         \
-     { png_uint_16 temp = (png_uint_16)((png_uint_16)(fg) \
-           * (png_uint_16)(alpha)                         \
-           + (png_uint_16)(bg)*(png_uint_16)(255          \
-           - (png_uint_16)(alpha)) + 128);                \
-       (composite) = (png_byte)(((temp + (temp >> 8)) >> 8) & 0xff); }
+#  define png_composite(composite, fg, alpha, bg)        \
+   {                                                     \
+      png_uint_16 temp = (png_uint_16)((png_uint_16)(fg) \
+          * (png_uint_16)(alpha)                         \
+          + (png_uint_16)(bg)*(png_uint_16)(255          \
+          - (png_uint_16)(alpha)) + 128);                \
+      (composite) = (png_byte)(((temp + (temp >> 8)) >> 8) & 0xff); \
+   }
 
-#  define png_composite_16(composite, fg, alpha, bg)       \
-     { png_uint_32 temp = (png_uint_32)((png_uint_32)(fg)  \
-           * (png_uint_32)(alpha)                          \
-           + (png_uint_32)(bg)*(65535                      \
-           - (png_uint_32)(alpha)) + 32768);               \
-       (composite) = (png_uint_16)(0xffff & ((temp + (temp >> 16)) >> 16)); }
+#  define png_composite_16(composite, fg, alpha, bg)     \
+   {                                                     \
+      png_uint_32 temp = (png_uint_32)((png_uint_32)(fg) \
+          * (png_uint_32)(alpha)                         \
+          + (png_uint_32)(bg)*(65535                     \
+          - (png_uint_32)(alpha)) + 32768);              \
+      (composite) = (png_uint_16)(0xffff & ((temp + (temp >> 16)) >> 16)); \
+   }
 
 #else  /* Standard method using integer division */
 
-#  define png_composite(composite, fg, alpha, bg)                        \
-     (composite) =                                                       \
-         (png_byte)(0xff & (((png_uint_16)(fg) * (png_uint_16)(alpha) +  \
-         (png_uint_16)(bg) * (png_uint_16)(255 - (png_uint_16)(alpha)) + \
-         127) / 255))
+#  define png_composite(composite, fg, alpha, bg)                      \
+   (composite) =                                                       \
+       (png_byte)(0xff & (((png_uint_16)(fg) * (png_uint_16)(alpha) +  \
+       (png_uint_16)(bg) * (png_uint_16)(255 - (png_uint_16)(alpha)) + \
+       127) / 255))
 
-#  define png_composite_16(composite, fg, alpha, bg)                         \
-     (composite) =                                                           \
-         (png_uint_16)(0xffff & (((png_uint_32)(fg) * (png_uint_32)(alpha) + \
-         (png_uint_32)(bg)*(png_uint_32)(65535 - (png_uint_32)(alpha)) +     \
-         32767) / 65535))
+#  define png_composite_16(composite, fg, alpha, bg)                       \
+   (composite) =                                                           \
+       (png_uint_16)(0xffff & (((png_uint_32)(fg) * (png_uint_32)(alpha) + \
+       (png_uint_32)(bg)*(png_uint_32)(65535 - (png_uint_32)(alpha)) +     \
+       32767) / 65535))
 #endif /* READ_COMPOSITE_NODIV */
 
 #ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
@@ -2592,38 +2597,38 @@
  * format for negative values, which is almost certainly true.
  */
 #  define PNG_get_uint_32(buf) \
-     (((png_uint_32)(*(buf)) << 24) + \
-      ((png_uint_32)(*((buf) + 1)) << 16) + \
-      ((png_uint_32)(*((buf) + 2)) << 8) + \
-      ((png_uint_32)(*((buf) + 3))))
+   (((png_uint_32)(*(buf)) << 24) + \
+    ((png_uint_32)(*((buf) + 1)) << 16) + \
+    ((png_uint_32)(*((buf) + 2)) << 8) + \
+    ((png_uint_32)(*((buf) + 3))))
 
    /* From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
     * function) incorrectly returned a value of type png_uint_32.
     */
 #  define PNG_get_uint_16(buf) \
-     ((png_uint_16) \
-      (((unsigned int)(*(buf)) << 8) + \
-       ((unsigned int)(*((buf) + 1)))))
+   ((png_uint_16) \
+    (((unsigned int)(*(buf)) << 8) + \
+    ((unsigned int)(*((buf) + 1)))))
 
 #  define PNG_get_int_32(buf) \
-     ((png_int_32)((*(buf) & 0x80) \
-      ? -((png_int_32)(((png_get_uint_32(buf)^0xffffffffU)+1U)&0x7fffffffU)) \
-      : (png_int_32)png_get_uint_32(buf)))
+   ((png_int_32)((*(buf) & 0x80) \
+    ? -((png_int_32)(((png_get_uint_32(buf)^0xffffffffU)+1U)&0x7fffffffU)) \
+    : (png_int_32)png_get_uint_32(buf)))
 
-   /* If PNG_PREFIX is defined the same thing as below happens in pnglibconf.h,
-    * but defining a macro name prefixed with PNG_PREFIX.
-    */
+/* If PNG_PREFIX is defined the same thing as below happens in pnglibconf.h,
+ * but defining a macro name prefixed with PNG_PREFIX.
+ */
 #  ifndef PNG_PREFIX
-#     define png_get_uint_32(buf) PNG_get_uint_32(buf)
-#     define png_get_uint_16(buf) PNG_get_uint_16(buf)
-#     define png_get_int_32(buf)  PNG_get_int_32(buf)
+#    define png_get_uint_32(buf) PNG_get_uint_32(buf)
+#    define png_get_uint_16(buf) PNG_get_uint_16(buf)
+#    define png_get_int_32(buf)  PNG_get_int_32(buf)
 #  endif
 #else
 #  ifdef PNG_PREFIX
-      /* No macros; revert to the (redefined) function */
-#     define PNG_get_uint_32 (png_get_uint_32)
-#     define PNG_get_uint_16 (png_get_uint_16)
-#     define PNG_get_int_32  (png_get_int_32)
+   /* No macros; revert to the (redefined) function */
+#    define PNG_get_uint_32 (png_get_uint_32)
+#    define PNG_get_uint_16 (png_get_uint_16)
+#    define PNG_get_int_32  (png_get_int_32)
 #  endif
 #endif
 
@@ -3171,9 +3176,9 @@
 #define PNG_IMAGE_PNG_SIZE_MAX_(image, image_size)\
    ((8U/*sig*/+25U/*IHDR*/+16U/*gAMA*/+44U/*cHRM*/+12U/*IEND*/+\
     (((image).format&PNG_FORMAT_FLAG_COLORMAP)?/*colormap: PLTE, tRNS*/\
-     12U+3U*(image).colormap_entries/*PLTE data*/+\
-     (((image).format&PNG_FORMAT_FLAG_ALPHA)?\
-      12U/*tRNS*/+(image).colormap_entries:0U):0U)+\
+    12U+3U*(image).colormap_entries/*PLTE data*/+\
+    (((image).format&PNG_FORMAT_FLAG_ALPHA)?\
+    12U/*tRNS*/+(image).colormap_entries:0U):0U)+\
     12U)+(12U*((image_size)/PNG_ZBUF_SIZE))/*IDAT*/+(image_size))
    /* A helper for the following macro; if your compiler cannot handle the
     * following macro use this one with the result of
diff --git a/pngconf.h b/pngconf.h
index b0ccc8c..9da691d 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,9 +1,9 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.6.23, June 9, 2016
+ * libpng version 1.6.24, August 4, 2016
  *
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -188,27 +188,27 @@
    * compatible with GCC or Visual C because of different calling conventions.
    */
 #  if PNG_API_RULE == 2
-    /* If this line results in an error, either because __watcall is not
-     * understood or because of a redefine just below you cannot use *this*
-     * build of the library with the compiler you are using.  *This* build was
-     * build using Watcom and applications must also be built using Watcom!
-     */
+   /* If this line results in an error, either because __watcall is not
+    * understood or because of a redefine just below you cannot use *this*
+    * build of the library with the compiler you are using.  *This* build was
+    * build using Watcom and applications must also be built using Watcom!
+    */
 #    define PNGCAPI __watcall
 #  endif
 
 #  if defined(__GNUC__) || (defined(_MSC_VER) && (_MSC_VER >= 800))
 #    define PNGCAPI __cdecl
 #    if PNG_API_RULE == 1
-       /* If this line results in an error __stdcall is not understood and
-        * PNG_API_RULE should not have been set to '1'.
-        */
+   /* If this line results in an error __stdcall is not understood and
+    * PNG_API_RULE should not have been set to '1'.
+    */
 #      define PNGAPI __stdcall
 #    endif
 #  else
-    /* An older compiler, or one not detected (erroneously) above,
-     * if necessary override on the command line to get the correct
-     * variants for the compiler.
-     */
+   /* An older compiler, or one not detected (erroneously) above,
+    * if necessary override on the command line to get the correct
+    * variants for the compiler.
+    */
 #    ifndef PNGCAPI
 #      define PNGCAPI _cdecl
 #    endif
@@ -225,10 +225,10 @@
 
 #  if (defined(_MSC_VER) && _MSC_VER < 800) ||\
       (defined(__BORLANDC__) && __BORLANDC__ < 0x500)
-    /* older Borland and MSC
-     * compilers used '__export' and required this to be after
-     * the type.
-     */
+   /* older Borland and MSC
+    * compilers used '__export' and required this to be after
+    * the type.
+    */
 #    ifndef PNG_EXPORT_TYPE
 #      define PNG_EXPORT_TYPE(type) type PNG_IMPEXP
 #    endif
@@ -244,9 +244,9 @@
 #  if (defined(__IBMC__) || defined(__IBMCPP__)) && defined(__OS2__)
 #    define PNGAPI _System
 #  else /* !Windows/x86 && !OS/2 */
-    /* Use the defaults, or define PNG*API on the command line (but
-     * this will have to be done for every compile!)
-     */
+   /* Use the defaults, or define PNG*API on the command line (but
+    * this will have to be done for every compile!)
+    */
 #  endif /* other system, !OS/2 */
 #endif /* !Windows/x86 */
 
@@ -267,7 +267,7 @@
  */
 #ifndef PNG_IMPEXP
 #  if defined(PNG_USE_DLL) && defined(PNG_DLL_IMPORT)
-     /* This forces use of a DLL, disallowing static linking */
+   /* This forces use of a DLL, disallowing static linking */
 #    define PNG_IMPEXP PNG_DLL_IMPORT
 #  endif
 
@@ -340,7 +340,7 @@
    * less efficient code.
    */
 #  if defined(__clang__) && defined(__has_attribute)
-     /* Clang defines both __clang__ and __GNUC__. Check __clang__ first. */
+   /* Clang defines both __clang__ and __GNUC__. Check __clang__ first. */
 #    if !defined(PNG_USE_RESULT) && __has_attribute(__warn_unused_result__)
 #      define PNG_USE_RESULT __attribute__((__warn_unused_result__))
 #    endif
diff --git a/pngerror.c b/pngerror.c
index 3fc8092..f13b764 100644
--- a/pngerror.c
+++ b/pngerror.c
@@ -1,8 +1,8 @@
 
 /* pngerror.c - stub functions for i/o and memory allocation
  *
- * Last changed in libpng 1.6.15 [November 20, 2014]
- * Copyright (c) 1998-2002,2004,2006-2014 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -26,7 +26,7 @@
 #ifdef PNG_WARNINGS_SUPPORTED
 static void /* PRIVATE */
 png_default_warning PNGARG((png_const_structrp png_ptr,
-   png_const_charp warning_message));
+    png_const_charp warning_message));
 #endif /* WARNINGS */
 
 /* This function is called whenever there is a fatal error.  This function
@@ -37,7 +37,7 @@
 #ifdef PNG_ERROR_TEXT_SUPPORTED
 PNG_FUNCTION(void,PNGAPI
 png_error,(png_const_structrp png_ptr, png_const_charp error_message),
-   PNG_NORETURN)
+    PNG_NORETURN)
 {
 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
    char msg[16];
@@ -65,18 +65,18 @@
 
             else
                error_message += offset;
-      }
-
-      else
-      {
-         if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
-         {
-            msg[0] = '0';
-            msg[1] = '\0';
-            error_message = msg;
          }
-       }
-     }
+
+         else
+         {
+            if ((png_ptr->flags & PNG_FLAG_STRIP_ERROR_TEXT) != 0)
+            {
+               msg[0] = '0';
+               msg[1] = '\0';
+               error_message = msg;
+            }
+         }
+      }
    }
 #endif
    if (png_ptr != NULL && png_ptr->error_fn != NULL)
@@ -110,7 +110,7 @@
  */
 size_t
 png_safecat(png_charp buffer, size_t bufsize, size_t pos,
-   png_const_charp string)
+    png_const_charp string)
 {
    if (buffer != NULL && pos < bufsize)
    {
@@ -131,7 +131,7 @@
  */
 png_charp
 png_format_number(png_const_charp start, png_charp end, int format,
-   png_alloc_size_t number)
+    png_alloc_size_t number)
 {
    int count = 0;    /* number of digits output */
    int mincount = 1; /* minimum number required */
@@ -233,7 +233,7 @@
    }
    if (png_ptr != NULL && png_ptr->warning_fn != NULL)
       (*(png_ptr->warning_fn))(png_constcast(png_structrp,png_ptr),
-         warning_message + offset);
+          warning_message + offset);
    else
       png_default_warning(png_ptr, warning_message + offset);
 }
@@ -245,7 +245,7 @@
  */
 void
 png_warning_parameter(png_warning_parameters p, int number,
-   png_const_charp string)
+    png_const_charp string)
 {
    if (number > 0 && number <= PNG_WARNING_PARAMETER_COUNT)
       (void)png_safecat(p[number-1], (sizeof p[number-1]), 0, string);
@@ -253,7 +253,7 @@
 
 void
 png_warning_parameter_unsigned(png_warning_parameters p, int number, int format,
-   png_alloc_size_t value)
+    png_alloc_size_t value)
 {
    char buffer[PNG_NUMBER_BUFFER_SIZE];
    png_warning_parameter(p, number, PNG_FORMAT_NUMBER(buffer, format, value));
@@ -261,7 +261,7 @@
 
 void
 png_warning_parameter_signed(png_warning_parameters p, int number, int format,
-   png_int_32 value)
+    png_int_32 value)
 {
    png_alloc_size_t u;
    png_charp str;
@@ -282,7 +282,7 @@
 
 void
 png_formatted_warning(png_const_structrp png_ptr, png_warning_parameters p,
-   png_const_charp message)
+    png_const_charp message)
 {
    /* The internal buffer is just 192 bytes - enough for all our messages,
     * overflow doesn't happen because this code checks!  If someone figures
@@ -391,10 +391,10 @@
 void /* PRIVATE */
 png_app_warning(png_const_structrp png_ptr, png_const_charp error_message)
 {
-  if ((png_ptr->flags & PNG_FLAG_APP_WARNINGS_WARN) != 0)
-     png_warning(png_ptr, error_message);
-  else
-     png_error(png_ptr, error_message);
+   if ((png_ptr->flags & PNG_FLAG_APP_WARNINGS_WARN) != 0)
+      png_warning(png_ptr, error_message);
+   else
+      png_error(png_ptr, error_message);
 
 #  ifndef PNG_ERROR_TEXT_SUPPORTED
       PNG_UNUSED(error_message)
@@ -404,10 +404,10 @@
 void /* PRIVATE */
 png_app_error(png_const_structrp png_ptr, png_const_charp error_message)
 {
-  if ((png_ptr->flags & PNG_FLAG_APP_ERRORS_WARN) != 0)
-     png_warning(png_ptr, error_message);
-  else
-     png_error(png_ptr, error_message);
+   if ((png_ptr->flags & PNG_FLAG_APP_ERRORS_WARN) != 0)
+      png_warning(png_ptr, error_message);
+   else
+      png_error(png_ptr, error_message);
 
 #  ifndef PNG_ERROR_TEXT_SUPPORTED
       PNG_UNUSED(error_message)
@@ -478,7 +478,7 @@
 #if defined(PNG_READ_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
 PNG_FUNCTION(void,PNGAPI
 png_chunk_error,(png_const_structrp png_ptr, png_const_charp error_message),
-   PNG_NORETURN)
+    PNG_NORETURN)
 {
    char msg[18+PNG_MAX_ERROR_TEXT];
    if (png_ptr == NULL)
@@ -620,7 +620,7 @@
       else
       {
          png_ptr->jmp_buf_ptr = png_voidcast(jmp_buf *,
-            png_malloc_warn(png_ptr, jmp_buf_size));
+             png_malloc_warn(png_ptr, jmp_buf_size));
 
          if (png_ptr->jmp_buf_ptr == NULL)
             return NULL; /* new NULL return on OOM */
@@ -709,7 +709,7 @@
  */
 static PNG_FUNCTION(void /* PRIVATE */,
 png_default_error,(png_const_structrp png_ptr, png_const_charp error_message),
-   PNG_NORETURN)
+    PNG_NORETURN)
 {
 #ifdef PNG_CONSOLE_IO_SUPPORTED
 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
@@ -883,7 +883,7 @@
     */
 PNG_FUNCTION(void /* PRIVATE */, (PNGCBAPI
 png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
-   PNG_NORETURN)
+    PNG_NORETURN)
 {
    const png_const_structrp png_ptr = png_nonconst_ptr;
    png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
@@ -906,7 +906,7 @@
       /* Missing longjmp buffer, the following is to help debugging: */
       {
          size_t pos = png_safecat(image->message, (sizeof image->message), 0,
-            "bad longjmp: ");
+             "bad longjmp: ");
          png_safecat(image->message, (sizeof image->message), pos,
              error_message);
       }
diff --git a/pngget.c b/pngget.c
index 14fc7be..b3c6863 100644
--- a/pngget.c
+++ b/pngget.c
@@ -1,8 +1,8 @@
 
 /* pngget.c - retrieval of values from info struct
  *
- * Last changed in libpng 1.6.17 [March 26, 2015]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -486,7 +486,7 @@
 #ifdef PNG_bKGD_SUPPORTED
 png_uint_32 PNGAPI
 png_get_bKGD(png_const_structrp png_ptr, png_inforp info_ptr,
-   png_color_16p *background)
+    png_color_16p *background)
 {
    if (png_ptr != NULL && info_ptr != NULL &&
        (info_ptr->valid & PNG_INFO_bKGD) != 0 &&
@@ -526,28 +526,28 @@
 
       if (white_x != NULL)
          *white_x = png_float(png_ptr,
-            info_ptr->colorspace.end_points_xy.whitex, "cHRM white X");
+             info_ptr->colorspace.end_points_xy.whitex, "cHRM white X");
       if (white_y != NULL)
          *white_y = png_float(png_ptr,
-            info_ptr->colorspace.end_points_xy.whitey, "cHRM white Y");
+             info_ptr->colorspace.end_points_xy.whitey, "cHRM white Y");
       if (red_x != NULL)
          *red_x = png_float(png_ptr, info_ptr->colorspace.end_points_xy.redx,
-            "cHRM red X");
+             "cHRM red X");
       if (red_y != NULL)
          *red_y = png_float(png_ptr, info_ptr->colorspace.end_points_xy.redy,
-            "cHRM red Y");
+             "cHRM red Y");
       if (green_x != NULL)
          *green_x = png_float(png_ptr,
-            info_ptr->colorspace.end_points_xy.greenx, "cHRM green X");
+             info_ptr->colorspace.end_points_xy.greenx, "cHRM green X");
       if (green_y != NULL)
          *green_y = png_float(png_ptr,
-            info_ptr->colorspace.end_points_xy.greeny, "cHRM green Y");
+             info_ptr->colorspace.end_points_xy.greeny, "cHRM green Y");
       if (blue_x != NULL)
          *blue_x = png_float(png_ptr, info_ptr->colorspace.end_points_xy.bluex,
-            "cHRM blue X");
+             "cHRM blue X");
       if (blue_y != NULL)
          *blue_y = png_float(png_ptr, info_ptr->colorspace.end_points_xy.bluey,
-            "cHRM blue Y");
+             "cHRM blue Y");
       return (PNG_INFO_cHRM);
    }
 
@@ -556,42 +556,42 @@
 
 png_uint_32 PNGAPI
 png_get_cHRM_XYZ(png_const_structrp png_ptr, png_const_inforp info_ptr,
-   double *red_X, double *red_Y, double *red_Z, double *green_X,
-   double *green_Y, double *green_Z, double *blue_X, double *blue_Y,
-   double *blue_Z)
+    double *red_X, double *red_Y, double *red_Z, double *green_X,
+    double *green_Y, double *green_Z, double *blue_X, double *blue_Y,
+    double *blue_Z)
 {
    if (png_ptr != NULL && info_ptr != NULL &&
-      (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
+       (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
    {
       png_debug1(1, "in %s retrieval function", "cHRM_XYZ(float)");
 
       if (red_X != NULL)
          *red_X = png_float(png_ptr, info_ptr->colorspace.end_points_XYZ.red_X,
-            "cHRM red X");
+             "cHRM red X");
       if (red_Y != NULL)
          *red_Y = png_float(png_ptr, info_ptr->colorspace.end_points_XYZ.red_Y,
-            "cHRM red Y");
+             "cHRM red Y");
       if (red_Z != NULL)
          *red_Z = png_float(png_ptr, info_ptr->colorspace.end_points_XYZ.red_Z,
-            "cHRM red Z");
+             "cHRM red Z");
       if (green_X != NULL)
          *green_X = png_float(png_ptr,
-            info_ptr->colorspace.end_points_XYZ.green_X, "cHRM green X");
+             info_ptr->colorspace.end_points_XYZ.green_X, "cHRM green X");
       if (green_Y != NULL)
          *green_Y = png_float(png_ptr,
-            info_ptr->colorspace.end_points_XYZ.green_Y, "cHRM green Y");
+             info_ptr->colorspace.end_points_XYZ.green_Y, "cHRM green Y");
       if (green_Z != NULL)
          *green_Z = png_float(png_ptr,
-            info_ptr->colorspace.end_points_XYZ.green_Z, "cHRM green Z");
+             info_ptr->colorspace.end_points_XYZ.green_Z, "cHRM green Z");
       if (blue_X != NULL)
          *blue_X = png_float(png_ptr,
-            info_ptr->colorspace.end_points_XYZ.blue_X, "cHRM blue X");
+             info_ptr->colorspace.end_points_XYZ.blue_X, "cHRM blue X");
       if (blue_Y != NULL)
          *blue_Y = png_float(png_ptr,
-            info_ptr->colorspace.end_points_XYZ.blue_Y, "cHRM blue Y");
+             info_ptr->colorspace.end_points_XYZ.blue_Y, "cHRM blue Y");
       if (blue_Z != NULL)
          *blue_Z = png_float(png_ptr,
-            info_ptr->colorspace.end_points_XYZ.blue_Z, "cHRM blue Z");
+             info_ptr->colorspace.end_points_XYZ.blue_Z, "cHRM blue Z");
       return (PNG_INFO_cHRM);
    }
 
@@ -681,8 +681,8 @@
    png_debug1(1, "in %s retrieval function", "gAMA");
 
    if (png_ptr != NULL && info_ptr != NULL &&
-      (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
-      file_gamma != NULL)
+       (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
+       file_gamma != NULL)
    {
       *file_gamma = info_ptr->colorspace.gamma;
       return (PNG_INFO_gAMA);
@@ -704,7 +704,7 @@
       file_gamma != NULL)
    {
       *file_gamma = png_float(png_ptr, info_ptr->colorspace.gamma,
-         "png_get_gAMA");
+          "png_get_gAMA");
       return (PNG_INFO_gAMA);
    }
 
@@ -901,7 +901,7 @@
        */
       *width = png_fixed(png_ptr, atof(info_ptr->scal_s_width), "sCAL width");
       *height = png_fixed(png_ptr, atof(info_ptr->scal_s_height),
-         "sCAL height");
+          "sCAL height");
       return (PNG_INFO_sCAL);
    }
 
diff --git a/pngmem.c b/pngmem.c
index 7bcfd00..6033bf2 100644
--- a/pngmem.c
+++ b/pngmem.c
@@ -1,8 +1,8 @@
 
 /* pngmem.c - stub functions for memory allocation
  *
- * Last changed in libpng 1.6.15 [November 20, 2014]
- * Copyright (c) 1998-2002,2004,2006-2014 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2014,2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -66,7 +66,7 @@
  */
 PNG_FUNCTION(png_voidp /* PRIVATE */,
 png_malloc_base,(png_const_structrp png_ptr, png_alloc_size_t size),
-   PNG_ALLOCATED)
+    PNG_ALLOCATED)
 {
    /* Moved to png_malloc_base from png_malloc_default in 1.6.0; the DOS
     * allocators have also been removed in 1.6.0, so any 16-bit system now has
@@ -107,7 +107,7 @@
  */
 static png_voidp
 png_malloc_array_checked(png_const_structrp png_ptr, int nelements,
-   size_t element_size)
+    size_t element_size)
 {
    png_alloc_size_t req = nelements; /* known to be > 0 */
 
@@ -120,7 +120,7 @@
 
 PNG_FUNCTION(png_voidp /* PRIVATE */,
 png_malloc_array,(png_const_structrp png_ptr, int nelements,
-   size_t element_size),PNG_ALLOCATED)
+    size_t element_size),PNG_ALLOCATED)
 {
    if (nelements <= 0 || element_size == 0)
       png_error(png_ptr, "internal error: array alloc");
@@ -130,7 +130,7 @@
 
 PNG_FUNCTION(png_voidp /* PRIVATE */,
 png_realloc_array,(png_const_structrp png_ptr, png_const_voidp old_array,
-   int old_elements, int add_elements, size_t element_size),PNG_ALLOCATED)
+    int old_elements, int add_elements, size_t element_size),PNG_ALLOCATED)
 {
    /* These are internal errors: */
    if (add_elements <= 0 || element_size == 0 || old_elements < 0 ||
@@ -143,7 +143,7 @@
    if (add_elements <= INT_MAX - old_elements)
    {
       png_voidp new_array = png_malloc_array_checked(png_ptr,
-         old_elements+add_elements, element_size);
+          old_elements+add_elements, element_size);
 
       if (new_array != NULL)
       {
@@ -154,7 +154,7 @@
             memcpy(new_array, old_array, element_size*(unsigned)old_elements);
 
          memset((char*)new_array + element_size*(unsigned)old_elements, 0,
-            element_size*(unsigned)add_elements);
+             element_size*(unsigned)add_elements);
 
          return new_array;
       }
@@ -187,7 +187,7 @@
 #ifdef PNG_USER_MEM_SUPPORTED
 PNG_FUNCTION(png_voidp,PNGAPI
 png_malloc_default,(png_const_structrp png_ptr, png_alloc_size_t size),
-   PNG_ALLOCATED PNG_DEPRECATED)
+    PNG_ALLOCATED PNG_DEPRECATED)
 {
    png_voidp ret;
 
@@ -210,7 +210,7 @@
  */
 PNG_FUNCTION(png_voidp,PNGAPI
 png_malloc_warn,(png_const_structrp png_ptr, png_alloc_size_t size),
-   PNG_ALLOCATED)
+    PNG_ALLOCATED)
 {
    if (png_ptr != NULL)
    {
diff --git a/pngpread.c b/pngpread.c
index ca300e7..794352f 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -1,7 +1,7 @@
 
 /* pngpread.c - read a png file in push mode
  *
- * Last changed in libpng 1.6.23 [June 9, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -77,11 +77,11 @@
 png_uint_32 PNGAPI
 png_process_data_skip(png_structrp png_ptr)
 {
-  /* TODO: Deprecate and remove this API.
-   * Somewhere the implementation of this seems to have been lost,
-   * or abandoned.  It was only to support some internal back-door access
-   * to png_struct) in libpng-1.4.x.
-   */
+/* TODO: Deprecate and remove this API.
+ * Somewhere the implementation of this seems to have been lost,
+ * or abandoned.  It was only to support some internal back-door access
+ * to png_struct) in libpng-1.4.x.
+ */
    png_app_warning(png_ptr,
 "png_process_data_skip is not implemented in any current version of libpng");
    return 0;
@@ -410,7 +410,7 @@
    {
       PNG_PUSH_SAVE_BUFFER_IF_FULL
       png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length,
-         PNG_HANDLE_CHUNK_AS_DEFAULT);
+          PNG_HANDLE_CHUNK_AS_DEFAULT);
    }
 
    png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
@@ -521,7 +521,7 @@
 
 void /* PRIVATE */
 png_push_restore_buffer(png_structrp png_ptr, png_bytep buffer,
-   png_size_t buffer_length)
+    png_size_t buffer_length)
 {
    png_ptr->current_buffer = buffer;
    png_ptr->current_buffer_size = buffer_length;
@@ -624,7 +624,7 @@
 
 void /* PRIVATE */
 png_process_IDAT_data(png_structrp png_ptr, png_bytep buffer,
-   png_size_t buffer_length)
+    png_size_t buffer_length)
 {
    /* The caller checks for a non-zero buffer length. */
    if (!(buffer_length > 0) || buffer == NULL)
@@ -782,7 +782,7 @@
    {
       if (png_ptr->pass < 6)
          png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
-            png_ptr->transformations);
+             png_ptr->transformations);
 
       switch (png_ptr->pass)
       {
@@ -1044,7 +1044,7 @@
 {
    if (png_ptr->row_fn != NULL)
       (*(png_ptr->row_fn))(png_ptr, row, png_ptr->row_number,
-         (int)png_ptr->pass);
+          (int)png_ptr->pass);
 }
 
 #ifdef PNG_READ_INTERLACING_SUPPORTED
diff --git a/pngpriv.h b/pngpriv.h
index 9338df3..fe3355d 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1,7 +1,7 @@
 
 /* pngpriv.h - private declarations for use inside libpng
  *
- * Last changed in libpng 1.6.22 [May 26, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -420,10 +420,10 @@
 
 #  if (defined(__MWERKS__) && defined(macintosh)) || defined(applec) || \
     defined(THINK_C) || defined(__SC__) || defined(TARGET_OS_MAC)
-     /* We need to check that <math.h> hasn't already been included earlier
-      * as it seems it doesn't agree with <fp.h>, yet we should really use
-      * <fp.h> if possible.
-      */
+   /* We need to check that <math.h> hasn't already been included earlier
+    * as it seems it doesn't agree with <fp.h>, yet we should really use
+    * <fp.h> if possible.
+    */
 #    if !defined(__MATH_H__) && !defined(__MATH_H) && !defined(__cmath__)
 #      include <fp.h>
 #    endif
@@ -431,9 +431,9 @@
 #    include <math.h>
 #  endif
 #  if defined(_AMIGA) && defined(__SASC) && defined(_M68881)
-     /* Amiga SAS/C: We must include builtin FPU functions when compiling using
-      * MATH=68881
-      */
+   /* Amiga SAS/C: We must include builtin FPU functions when compiling using
+    * MATH=68881
+    */
 #    include <m68881.h>
 #  endif
 #endif
@@ -1025,7 +1025,7 @@
 #ifdef PNG_WRITE_cHRM_SUPPORTED
 PNG_INTERNAL_FUNCTION(void,png_write_cHRM_fixed,(png_structrp png_ptr,
     const png_xy *xy), PNG_EMPTY);
-    /* The xy value must have been previously validated */
+   /* The xy value must have been previously validated */
 #endif
 
 #ifdef PNG_WRITE_sRGB_SUPPORTED
@@ -1174,6 +1174,7 @@
 PNG_INTERNAL_FUNCTION(void,png_read_filter_row,(png_structrp pp, png_row_infop
     row_info, png_bytep row, png_const_bytep prev_row, int filter),PNG_EMPTY);
 
+#if PNG_ARM_NEON_OPT > 0
 PNG_INTERNAL_FUNCTION(void,png_read_filter_row_up_neon,(png_row_infop row_info,
     png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_read_filter_row_sub3_neon,(png_row_infop
@@ -1188,6 +1189,7 @@
     row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_read_filter_row_paeth4_neon,(png_row_infop
     row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
+#endif
 
 /* Choose the best filter to use and filter the row data */
 PNG_INTERNAL_FUNCTION(void,png_write_find_filter,(png_structrp png_ptr,
@@ -1413,7 +1415,7 @@
 PNG_INTERNAL_FUNCTION(void,png_push_have_end,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_have_row,(png_structrp png_ptr,
-     png_bytep row),PNG_EMPTY);
+    png_bytep row),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_read_end,(png_structrp png_ptr,
     png_inforp info_ptr),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_process_some_data,(png_structrp png_ptr,
@@ -1452,13 +1454,13 @@
 
 PNG_INTERNAL_FUNCTION(void,png_colorspace_sync_info,(png_const_structrp png_ptr,
     png_inforp info_ptr), PNG_EMPTY);
-    /* Synchronize the info 'valid' flags with the colorspace */
+   /* Synchronize the info 'valid' flags with the colorspace */
 
 PNG_INTERNAL_FUNCTION(void,png_colorspace_sync,(png_const_structrp png_ptr,
     png_inforp info_ptr), PNG_EMPTY);
-    /* Copy the png_struct colorspace to the info_struct and call the above to
-     * synchronize the flags.  Checks for NULL info_ptr and does nothing.
-     */
+   /* Copy the png_struct colorspace to the info_struct and call the above to
+    * synchronize the flags.  Checks for NULL info_ptr and does nothing.
+    */
 #endif
 
 /* Added at libpng version 1.4.0 */
@@ -1913,8 +1915,10 @@
     * the builder of libpng passes the definition of PNG_FILTER_OPTIMIZATIONS in
     * CFLAGS in place of CPPFLAGS *and* uses symbol prefixing.
     */
+#  if PNG_ARM_NEON_OPT > 0
 PNG_INTERNAL_FUNCTION(void, png_init_filter_functions_neon,
    (png_structp png_ptr, unsigned int bpp), PNG_EMPTY);
+#  endif
 #endif
 
 PNG_INTERNAL_FUNCTION(png_uint_32, png_check_keyword, (png_structrp png_ptr,
diff --git a/pngread.c b/pngread.c
index 0ff6238..1000326 100644
--- a/pngread.c
+++ b/pngread.c
@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Last changed in libpng 1.6.23 [June 9, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -28,10 +28,10 @@
 {
 #ifndef PNG_USER_MEM_SUPPORTED
    png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
-      error_fn, warn_fn, NULL, NULL, NULL);
+        error_fn, warn_fn, NULL, NULL, NULL);
 #else
    return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
-       warn_fn, NULL, NULL, NULL);
+        warn_fn, NULL, NULL, NULL);
 }
 
 /* Alternate create PNG structure for reading, and allocate any memory
@@ -43,7 +43,7 @@
     png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
 {
    png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
-      error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
+       error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
 #endif /* USER_MEM */
 
    if (png_ptr != NULL)
@@ -252,7 +252,7 @@
 
       else
          png_handle_unknown(png_ptr, info_ptr, length,
-            PNG_HANDLE_CHUNK_AS_DEFAULT);
+             PNG_HANDLE_CHUNK_AS_DEFAULT);
    }
 }
 #endif /* SEQUENTIAL_READ */
@@ -279,7 +279,7 @@
       /* New in 1.6.0 this avoids the bug of doing the initializations twice */
       else
          png_app_error(png_ptr,
-            "png_read_update_info/png_start_read_image: duplicate call");
+             "png_read_update_info/png_start_read_image: duplicate call");
    }
 }
 
@@ -302,7 +302,7 @@
       /* New in 1.6.0 this avoids the bug of doing the initializations twice */
       else
          png_app_error(png_ptr,
-            "png_start_read_image/png_read_update_info: duplicate call");
+             "png_start_read_image/png_read_update_info: duplicate call");
    }
 }
 #endif /* SEQUENTIAL_READ */
@@ -540,7 +540,7 @@
    {
       if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
          png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
-            png_ptr->prev_row + 1, png_ptr->row_buf[0]);
+             png_ptr->prev_row + 1, png_ptr->row_buf[0]);
       else
          png_error(png_ptr, "bad adaptive filter value");
    }
@@ -584,7 +584,7 @@
    {
       if (png_ptr->pass < 6)
          png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
-            png_ptr->transformations);
+             png_ptr->transformations);
 
       if (dsp_row != NULL)
          png_combine_row(png_ptr, dsp_row, 1/*display*/);
@@ -719,7 +719,7 @@
           * but the caller should do it!
           */
          png_warning(png_ptr, "Interlace handling should be turned on when "
-            "using png_read_image");
+             "using png_read_image");
          /* Make sure this is set correctly */
          png_ptr->num_rows = png_ptr->height;
       }
@@ -779,8 +779,8 @@
 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
    /* Report invalid palette index; added at libng-1.5.10 */
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
-      png_ptr->num_palette_max > png_ptr->num_palette)
-     png_benign_error(png_ptr, "Read palette index exceeding num_palette");
+       png_ptr->num_palette_max > png_ptr->num_palette)
+      png_benign_error(png_ptr, "Read palette index exceeding num_palette");
 #endif
 
    do
@@ -919,7 +919,7 @@
 
       else
          png_handle_unknown(png_ptr, info_ptr, length,
-            PNG_HANDLE_CHUNK_AS_DEFAULT);
+             PNG_HANDLE_CHUNK_AS_DEFAULT);
    } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
 }
 #endif /* SEQUENTIAL_READ */
@@ -1030,8 +1030,7 @@
 #ifdef PNG_INFO_IMAGE_SUPPORTED
 void PNGAPI
 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
-                           int transforms,
-                           voidp params)
+    int transforms, voidp params)
 {
    if (png_ptr == NULL || info_ptr == NULL)
       return;
@@ -1307,7 +1306,7 @@
          if (info_ptr != NULL)
          {
             png_controlp control = png_voidcast(png_controlp,
-               png_malloc_warn(png_ptr, (sizeof *control)));
+                png_malloc_warn(png_ptr, (sizeof *control)));
 
             if (control != NULL)
             {
@@ -1470,12 +1469,12 @@
 
       else
          return png_image_error(image,
-            "png_image_begin_read_from_stdio: invalid argument");
+             "png_image_begin_read_from_stdio: invalid argument");
    }
 
    else if (image != NULL)
       return png_image_error(image,
-         "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
+          "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
 
    return 0;
 }
@@ -1508,12 +1507,12 @@
 
       else
          return png_image_error(image,
-            "png_image_begin_read_from_file: invalid argument");
+             "png_image_begin_read_from_file: invalid argument");
    }
 
    else if (image != NULL)
       return png_image_error(image,
-         "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
+          "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
 
    return 0;
 }
@@ -1550,7 +1549,7 @@
 }
 
 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
-   png_const_voidp memory, png_size_t size)
+    png_const_voidp memory, png_size_t size)
 {
    if (image != NULL && image->version == PNG_IMAGE_VERSION)
    {
@@ -1573,12 +1572,12 @@
 
       else
          return png_image_error(image,
-            "png_image_begin_read_from_memory: invalid argument");
+             "png_image_begin_read_from_memory: invalid argument");
    }
 
    else if (image != NULL)
       return png_image_error(image,
-         "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
+          "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
 
    return 0;
 }
@@ -1624,12 +1623,12 @@
         * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
         */
        png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
-         NULL, -1);
+           NULL, -1);
 
        /* But do not ignore image data handling chunks */
        png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
-         chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
-    }
+           chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
+   }
 }
 
 #  define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
@@ -1696,7 +1695,7 @@
 #ifdef __GNUC__
       default:
          png_error(display->image->opaque->png_ptr,
-            "unexpected encoding (internal error)");
+             "unexpected encoding (internal error)");
 #endif
    }
 
@@ -1705,8 +1704,8 @@
 
 static png_uint_32
 png_colormap_compose(png_image_read_control *display,
-   png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
-   png_uint_32 background, int encoding)
+    png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
+    png_uint_32 background, int encoding)
 {
    /* The file value is composed on the background, the background has the given
     * encoding and so does the result, the file is encoded with P_FILE and the
@@ -1742,14 +1741,14 @@
  */
 static void
 png_create_colormap_entry(png_image_read_control *display,
-   png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
-   png_uint_32 alpha, int encoding)
+    png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
+    png_uint_32 alpha, int encoding)
 {
    png_imagep image = display->image;
    const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
-      P_LINEAR : P_sRGB;
+       P_LINEAR : P_sRGB;
    const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
-      (red != green || green != blue);
+       (red != green || green != blue);
 
    if (ip > 255)
       png_error(image->opaque->png_ptr, "color-map index out of range");
@@ -2029,7 +2028,7 @@
 
       for (g=0; g<6; ++g)
          png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
-            P_sRGB);
+             P_sRGB);
    }
 
    return i;
@@ -2053,7 +2052,7 @@
 
          for (b=0; b<6; ++b)
             png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
-               P_sRGB);
+                P_sRGB);
       }
    }
 
@@ -2105,7 +2104,7 @@
 
       else if (display->background == NULL /* no way to remove it */)
          png_error(png_ptr,
-            "a background color must be supplied to remove alpha/transparency");
+             "background color must be supplied to remove alpha/transparency");
 
       /* Get a copy of the background color (this avoids repeating the checks
        * below.)  The encoding is 8-bit sRGB or 16-bit linear, depending on the
@@ -2200,7 +2199,7 @@
                 */
                if (i != trans)
                   png_create_colormap_entry(display, i, val, val, val, 255,
-                     P_FILE/*8-bit with file gamma*/);
+                      P_FILE/*8-bit with file gamma*/);
 
                /* Else this entry is transparent.  The colors don't matter if
                 * there is an alpha channel (back_alpha == 0), but it does no
@@ -2212,7 +2211,7 @@
                 */
                else
                   png_create_colormap_entry(display, i, back_r, back_g, back_b,
-                     back_alpha, output_encoding);
+                      back_alpha, output_encoding);
             }
 
             /* We need libpng to preserve the original encoding. */
@@ -2277,7 +2276,7 @@
                          * matches.
                          */
                         png_create_colormap_entry(display, gray, back_g, back_g,
-                           back_g, 65535, P_LINEAR);
+                            back_g, 65535, P_LINEAR);
                      }
 
                      /* The background passed to libpng, however, must be the
@@ -2291,8 +2290,8 @@
                       * doesn't.
                       */
                      png_set_background_fixed(png_ptr, &c,
-                        PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
-                        0/*gamma: not used*/);
+                         PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+                         0/*gamma: not used*/);
 
                      output_processing = PNG_CMAP_NONE;
                      break;
@@ -2322,7 +2321,7 @@
                 * background color at full precision.
                 */
                png_create_colormap_entry(display, 254, back_r, back_g, back_b,
-                  back_alpha, output_encoding);
+                   back_alpha, output_encoding);
             }
 
             else
@@ -2390,7 +2389,7 @@
 
                   /* And make sure the corresponding palette entry matches. */
                   png_create_colormap_entry(display, gray, back_g, back_g,
-                     back_g, 65535, P_LINEAR);
+                      back_g, 65535, P_LINEAR);
                }
 
                /* The background passed to libpng, however, must be the sRGB
@@ -2400,8 +2399,8 @@
                c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
 
                png_set_background_fixed(png_ptr, &c,
-                  PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
-                  0/*gamma: not used*/);
+                   PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+                   0/*gamma: not used*/);
 
                output_processing = PNG_CMAP_NONE;
             }
@@ -2421,7 +2420,7 @@
                {
                   png_uint_32 gray = (i * 256 + 115) / 231;
                   png_create_colormap_entry(display, i++, gray, gray, gray,
-                     255, P_sRGB);
+                      255, P_sRGB);
                }
 
                /* NOTE: this preserves the full precision of the application
@@ -2430,13 +2429,13 @@
                background_index = i;
                png_create_colormap_entry(display, i++, back_r, back_g, back_b,
 #ifdef __COVERITY__
-                 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
-                  * here.
-                  */ 255U,
+                   /* Coverity claims that output_encoding
+                    * cannot be 2 (P_LINEAR) here.
+                    */ 255U,
 #else
-                  output_encoding == P_LINEAR ? 65535U : 255U,
+                    output_encoding == P_LINEAR ? 65535U : 255U,
 #endif
-                  output_encoding);
+                    output_encoding);
 
                /* For non-opaque input composite on the sRGB background - this
                 * requires inverting the encoding for each component.  The input
@@ -2474,9 +2473,9 @@
                      png_uint_32 gray = png_sRGB_table[g*51] * alpha;
 
                      png_create_colormap_entry(display, i++,
-                        PNG_sRGB_FROM_LINEAR(gray + back_rx),
-                        PNG_sRGB_FROM_LINEAR(gray + back_gx),
-                        PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
+                         PNG_sRGB_FROM_LINEAR(gray + back_rx),
+                         PNG_sRGB_FROM_LINEAR(gray + back_gx),
+                         PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
                   }
                }
 
@@ -2502,7 +2501,7 @@
              * png_set_tRNS_to_alpha before png_set_background_fixed.
              */
             png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
-               -1);
+                -1);
             data_encoding = P_sRGB;
 
             /* The output will now be one or two 8-bit gray or gray+alpha
@@ -2578,13 +2577,13 @@
                         gray = png_sRGB_table[gray]; /* now P_LINEAR */
 
                      gray = PNG_DIV257(png_gamma_16bit_correct(gray,
-                        png_ptr->colorspace.gamma)); /* now P_FILE */
+                         png_ptr->colorspace.gamma)); /* now P_FILE */
 
                      /* And make sure the corresponding palette entry contains
                       * exactly the required sRGB value.
                       */
                      png_create_colormap_entry(display, gray, back_g, back_g,
-                        back_g, 0/*unused*/, output_encoding);
+                         back_g, 0/*unused*/, output_encoding);
                   }
 
                   else if (output_encoding == P_LINEAR)
@@ -2609,8 +2608,8 @@
                    */
                   expand_tRNS = 1;
                   png_set_background_fixed(png_ptr, &c,
-                     PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
-                     0/*gamma: not used*/);
+                      PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+                      0/*gamma: not used*/);
                }
 
                output_processing = PNG_CMAP_NONE;
@@ -2644,7 +2643,7 @@
 
                   /* Add a transparent entry. */
                   png_create_colormap_entry(display, cmap_entries, 255, 255,
-                     255, 0, P_sRGB);
+                      255, 0, P_sRGB);
 
                   /* This is stored as the background index for the processing
                    * algorithm.
@@ -2665,7 +2664,7 @@
                          */
                         for (b=0; b<256; b = (b << 1) | 0x7f)
                            png_create_colormap_entry(display, cmap_entries++,
-                              r, g, b, 128, P_sRGB);
+                               r, g, b, 128, P_sRGB);
                      }
                   }
 
@@ -2692,7 +2691,7 @@
                   cmap_entries = make_rgb_colormap(display);
 
                   png_create_colormap_entry(display, cmap_entries, back_r,
-                        back_g, back_b, 0/*unused*/, output_encoding);
+                      back_g, back_b, 0/*unused*/, output_encoding);
 
                   if (output_encoding == P_LINEAR)
                   {
@@ -2714,9 +2713,9 @@
                    * index.
                    */
                   if (memcmp((png_const_bytep)display->colormap +
-                        sample_size * cmap_entries,
-                     (png_const_bytep)display->colormap +
-                        sample_size * PNG_RGB_INDEX(r,g,b),
+                      sample_size * cmap_entries,
+                      (png_const_bytep)display->colormap +
+                          sample_size * PNG_RGB_INDEX(r,g,b),
                      sample_size) != 0)
                   {
                      /* The background color must be added. */
@@ -2734,13 +2733,13 @@
                             */
                            for (b=0; b<256; b = (b << 1) | 0x7f)
                               png_create_colormap_entry(display, cmap_entries++,
-                                 png_colormap_compose(display, r, P_sRGB, 128,
-                                    back_r, output_encoding),
-                                 png_colormap_compose(display, g, P_sRGB, 128,
-                                    back_g, output_encoding),
-                                 png_colormap_compose(display, b, P_sRGB, 128,
-                                    back_b, output_encoding),
-                                 0/*unused*/, output_encoding);
+                                  png_colormap_compose(display, r, P_sRGB, 128,
+                                      back_r, output_encoding),
+                                  png_colormap_compose(display, g, P_sRGB, 128,
+                                      back_g, output_encoding),
+                                  png_colormap_compose(display, b, P_sRGB, 128,
+                                      back_b, output_encoding),
+                                  0/*unused*/, output_encoding);
                         }
                      }
 
@@ -2758,8 +2757,8 @@
                      c.blue = (png_uint_16)back_b;
 
                      png_set_background_fixed(png_ptr, &c,
-                        PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
-                        0/*gamma: not used*/);
+                         PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+                         0/*gamma: not used*/);
 
                      output_processing = PNG_CMAP_RGB;
                   }
@@ -2811,7 +2810,7 @@
                {
                   if (trans[i] == 0)
                      png_create_colormap_entry(display, i, back_r, back_g,
-                        back_b, 0, output_encoding);
+                         back_b, 0, output_encoding);
 
                   else
                   {
@@ -2819,22 +2818,22 @@
                       * on the sRGB color in 'back'.
                       */
                      png_create_colormap_entry(display, i,
-                        png_colormap_compose(display, colormap[i].red, P_FILE,
-                           trans[i], back_r, output_encoding),
-                        png_colormap_compose(display, colormap[i].green, P_FILE,
-                           trans[i], back_g, output_encoding),
-                        png_colormap_compose(display, colormap[i].blue, P_FILE,
-                           trans[i], back_b, output_encoding),
-                        output_encoding == P_LINEAR ? trans[i] * 257U :
-                           trans[i],
-                        output_encoding);
+                         png_colormap_compose(display, colormap[i].red,
+                             P_FILE, trans[i], back_r, output_encoding),
+                         png_colormap_compose(display, colormap[i].green,
+                             P_FILE, trans[i], back_g, output_encoding),
+                         png_colormap_compose(display, colormap[i].blue,
+                             P_FILE, trans[i], back_b, output_encoding),
+                         output_encoding == P_LINEAR ? trans[i] * 257U :
+                             trans[i],
+                         output_encoding);
                   }
                }
 
                else
                   png_create_colormap_entry(display, i, colormap[i].red,
-                     colormap[i].green, colormap[i].blue,
-                     i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
+                      colormap[i].green, colormap[i].blue,
+                      i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
             }
 
             /* The PNG data may have indices packed in fewer than 8 bits, it
@@ -2924,7 +2923,7 @@
 png_image_read_and_map(png_voidp argument)
 {
    png_image_read_control *display = png_voidcast(png_image_read_control*,
-      argument);
+       argument);
    png_imagep image = display->image;
    png_structrp png_ptr = image->opaque->png_ptr;
    int passes;
@@ -3061,7 +3060,7 @@
 
                      if (alpha >= 196)
                         *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
-                           inrow[2]);
+                            inrow[2]);
 
                      else if (alpha < 64)
                         *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
@@ -3113,7 +3112,7 @@
 png_image_read_colormapped(png_voidp argument)
 {
    png_image_read_control *display = png_voidcast(png_image_read_control*,
-      argument);
+       argument);
    png_imagep image = display->image;
    png_controlp control = image->opaque;
    png_structrp png_ptr = control->png_ptr;
@@ -3246,7 +3245,7 @@
 png_image_read_composite(png_voidp argument)
 {
    png_image_read_control *display = png_voidcast(png_image_read_control*,
-      argument);
+       argument);
    png_imagep image = display->image;
    png_structrp png_ptr = image->opaque->png_ptr;
    int passes;
@@ -3373,7 +3372,7 @@
 png_image_read_background(png_voidp argument)
 {
    png_image_read_control *display = png_voidcast(png_image_read_control*,
-      argument);
+       argument);
    png_imagep image = display->image;
    png_structrp png_ptr = image->opaque->png_ptr;
    png_inforp info_ptr = image->opaque->info_ptr;
@@ -3433,8 +3432,7 @@
 
             for (pass = 0; pass < passes; ++pass)
             {
-               png_bytep        row = png_voidcast(png_bytep,
-                                                   display->first_row);
+               png_bytep row = png_voidcast(png_bytep, display->first_row);
                unsigned int     startx, stepx, stepy;
                png_uint_32      y;
 
@@ -3462,7 +3460,7 @@
                   for (; y<height; y += stepy)
                   {
                      png_bytep inrow = png_voidcast(png_bytep,
-                        display->local_row);
+                         display->local_row);
                      png_bytep outrow = first_row + y * step_row;
                      png_const_bytep end_row = outrow + width;
 
@@ -3507,7 +3505,7 @@
                   for (; y<height; y += stepy)
                   {
                      png_bytep inrow = png_voidcast(png_bytep,
-                        display->local_row);
+                         display->local_row);
                      png_bytep outrow = first_row + y * step_row;
                      png_const_bytep end_row = outrow + width;
 
@@ -3554,7 +3552,7 @@
           */
          {
             png_uint_16p first_row = png_voidcast(png_uint_16p,
-               display->first_row);
+                display->first_row);
             /* The division by two is safe because the caller passed in a
              * stride which was multiplied by 2 (below) to get row_bytes.
              */
@@ -3604,7 +3602,7 @@
 
                   /* Read the row, which is packed: */
                   png_read_row(png_ptr, png_voidcast(png_bytep,
-                     display->local_row), NULL);
+                      display->local_row), NULL);
                   inrow = png_voidcast(png_const_uint_16p, display->local_row);
 
                   /* Now do the pre-multiplication on each pixel in this row.
@@ -3653,7 +3651,7 @@
 png_image_read_direct(png_voidp argument)
 {
    png_image_read_control *display = png_voidcast(png_image_read_control*,
-      argument);
+       argument);
    png_imagep image = display->image;
    png_structrp png_ptr = image->opaque->png_ptr;
    png_inforp info_ptr = image->opaque->info_ptr;
@@ -3704,7 +3702,7 @@
                do_local_background = 1/*maybe*/;
 
             png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
-               PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
+                PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
          }
 
          change &= ~PNG_FORMAT_FLAG_COLOR;
@@ -3763,7 +3761,7 @@
           * final value.
           */
          if (png_muldiv(&gtest, output_gamma, png_ptr->colorspace.gamma,
-               PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
+             PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
             do_local_background = 0;
 
          else if (mode == PNG_ALPHA_STANDARD)
@@ -3826,8 +3824,8 @@
                 * pixels.
                 */
                png_set_background_fixed(png_ptr, &c,
-                  PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
-                  0/*gamma: not used*/);
+                   PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+                   0/*gamma: not used*/);
             }
 
             else /* compose on row: implemented below. */
@@ -4077,7 +4075,7 @@
 
 int PNGAPI
 png_image_finish_read(png_imagep image, png_const_colorp background,
-   void *buffer, png_int_32 row_stride, void *colormap)
+    void *buffer, png_int_32 row_stride, void *colormap)
 {
    if (image != NULL && image->version == PNG_IMAGE_VERSION)
    {
@@ -4087,6 +4085,12 @@
        */
       const unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
 
+      /* The following checks just the 'row_stride' calculation to ensure it
+       * fits in a signed 32-bit value.  Because channels/components can be
+       * either 1 or 2 bytes in size the length of a row can still overflow 32
+       * bits; this is just to verify that the 'row_stride' argument can be
+       * represented.
+       */
       if (image->width <= 0x7FFFFFFFU/channels) /* no overflow */
       {
          png_uint_32 check;
@@ -4101,13 +4105,30 @@
          else
             check = row_stride;
 
+         /* This verifies 'check', the absolute value of the actual stride
+          * passed in and detects overflow in the application calculation (i.e.
+          * if the app did actually pass in a non-zero 'row_stride'.
+          */
          if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
          {
             /* Now check for overflow of the image buffer calculation; this
              * limits the whole image size to 32 bits for API compatibility with
              * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
+             *
+             * The PNG_IMAGE_BUFFER_SIZE macro is:
+             *
+             *    (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
+             *
+             * And the component size is always 1 or 2, so make sure that the
+             * number of *bytes* that the application is saying are available
+             * does actually fit into a 32-bit number.
+             *
+             * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
+             * will be changed to use png_alloc_size_t; bigger images can be
+             * accomodated on 64-bit systems.
              */
-            if (image->height <= 0xFFFFFFFF/png_row_stride)
+            if (image->height <=
+                0xFFFFFFFFU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
             {
                if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
                   (image->colormap_entries > 0 && colormap != NULL))
@@ -4127,15 +4148,16 @@
                    * all the setup has already been done.
                    */
                   if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
-                     result = png_safe_execute(image,
-                                    png_image_read_colormap, &display) &&
-                              png_safe_execute(image,
-                                    png_image_read_colormapped, &display);
+                     result =
+                         png_safe_execute(image,
+                             png_image_read_colormap, &display) &&
+                             png_safe_execute(image,
+                             png_image_read_colormapped, &display);
 
                   else
                      result =
                         png_safe_execute(image,
-                              png_image_read_direct, &display);
+                            png_image_read_direct, &display);
 
                   png_image_free(image);
                   return result;
@@ -4143,27 +4165,27 @@
 
                else
                   return png_image_error(image,
-                     "png_image_finish_read[color-map]: no color-map");
+                      "png_image_finish_read[color-map]: no color-map");
             }
 
             else
                return png_image_error(image,
-                  "png_image_finish_read: image too large");
+                   "png_image_finish_read: image too large");
          }
 
          else
             return png_image_error(image,
-               "png_image_finish_read: invalid argument");
+                "png_image_finish_read: invalid argument");
       }
 
       else
          return png_image_error(image,
-            "png_image_finish_read: row_stride too large");
+             "png_image_finish_read: row_stride too large");
    }
 
    else if (image != NULL)
       return png_image_error(image,
-         "png_image_finish_read: damaged PNG_IMAGE_VERSION");
+          "png_image_finish_read: damaged PNG_IMAGE_VERSION");
 
    return 0;
 }
diff --git a/pngrio.c b/pngrio.c
index 5101d54..7e26e85 100644
--- a/pngrio.c
+++ b/pngrio.c
@@ -1,8 +1,8 @@
 
 /* pngrio.c - functions for data input
  *
- * Last changed in libpng 1.6.17 [March 26, 2015]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -85,7 +85,7 @@
  */
 void PNGAPI
 png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
-   png_rw_ptr read_data_fn)
+    png_rw_ptr read_data_fn)
 {
    if (png_ptr == NULL)
       return;
diff --git a/pngrtran.c b/pngrtran.c
index 3138147..748ffb3 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,7 +1,7 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.6.22 [May 26, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -48,7 +48,7 @@
 
       case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
          png_warning(png_ptr,
-            "Can't discard critical data on CRC error");
+             "Can't discard critical data on CRC error");
       case PNG_CRC_ERROR_QUIT:                                /* Error/quit */
 
       case PNG_CRC_DEFAULT:
@@ -101,7 +101,7 @@
    {
       if ((png_ptr->flags & PNG_FLAG_ROW_INIT) != 0)
          png_app_error(png_ptr,
-            "invalid after png_start_read_image or png_read_update_info");
+             "invalid after png_start_read_image or png_read_update_info");
 
       else if (need_IHDR && (png_ptr->mode & PNG_HAVE_IHDR) == 0)
          png_app_error(png_ptr, "invalid before the PNG header has been read");
@@ -209,7 +209,7 @@
 #if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
 static png_fixed_point
 translate_gamma_flags(png_structrp png_ptr, png_fixed_point output_gamma,
-   int is_screen)
+    int is_screen)
 {
    /* Check for flag values.  The main reason for having the old Mac value as a
     * flag is that it is pretty near impossible to work out what the correct
@@ -273,7 +273,7 @@
 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
 void PNGFAPI
 png_set_alpha_mode_fixed(png_structrp png_ptr, int mode,
-   png_fixed_point output_gamma)
+    png_fixed_point output_gamma)
 {
    int compose = 0;
    png_fixed_point file_gamma;
@@ -377,7 +377,7 @@
 
       if ((png_ptr->transformations & PNG_COMPOSE) != 0)
          png_error(png_ptr,
-            "conflicting calls to set alpha mode and background");
+             "conflicting calls to set alpha mode and background");
 
       png_ptr->transformations |= PNG_COMPOSE;
    }
@@ -388,7 +388,7 @@
 png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
 {
    png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
-      output_gamma));
+       output_gamma));
 }
 #  endif
 #endif
@@ -802,7 +802,7 @@
 #ifdef PNG_READ_GAMMA_SUPPORTED
 void PNGFAPI
 png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma,
-   png_fixed_point file_gamma)
+    png_fixed_point file_gamma)
 {
    png_debug(1, "in png_set_gamma_fixed");
 
@@ -844,7 +844,7 @@
 png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
 {
    png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
-      convert_gamma_value(png_ptr, file_gamma));
+       convert_gamma_value(png_ptr, file_gamma));
 }
 #  endif /* FLOATING_POINT */
 #endif /* READ_GAMMA */
@@ -990,7 +990,7 @@
        * that it just worked and get a memory overwrite.
        */
       png_error(png_ptr,
-        "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
+          "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
 
       /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
    }
@@ -1017,7 +1017,7 @@
       {
          if (red >= 0 && green >= 0)
             png_app_warning(png_ptr,
-               "ignoring out of range rgb_to_gray coefficients");
+                "ignoring out of range rgb_to_gray coefficients");
 
          /* Use the defaults, from the cHRM chunk if set, else the historical
           * values which are close to the sRGB/HDTV/ITU-Rec 709 values.  See
@@ -1026,7 +1026,7 @@
           * something has already provided a default.
           */
          if (png_ptr->rgb_to_gray_red_coeff == 0 &&
-            png_ptr->rgb_to_gray_green_coeff == 0)
+             png_ptr->rgb_to_gray_green_coeff == 0)
          {
             png_ptr->rgb_to_gray_red_coeff   = 6968;
             png_ptr->rgb_to_gray_green_coeff = 23434;
@@ -1043,10 +1043,10 @@
 
 void PNGAPI
 png_set_rgb_to_gray(png_structrp png_ptr, int error_action, double red,
-   double green)
+    double green)
 {
    png_set_rgb_to_gray_fixed(png_ptr, error_action,
-      png_fixed(png_ptr, red, "rgb to gray red coefficient"),
+       png_fixed(png_ptr, red, "rgb to gray red coefficient"),
       png_fixed(png_ptr, green, "rgb to gray green coefficient"));
 }
 #endif /* FLOATING POINT */
@@ -1303,7 +1303,7 @@
       {
          if (png_ptr->screen_gamma != 0) /* screen set too */
             gamma_correction = png_gamma_threshold(png_ptr->colorspace.gamma,
-               png_ptr->screen_gamma);
+                png_ptr->screen_gamma);
 
          else
             /* Assume the output matches the input; a long time default behavior
@@ -1584,7 +1584,7 @@
           */
          if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
             png_warning(png_ptr,
-               "libpng does not support gamma+background+rgb_to_gray");
+                "libpng does not support gamma+background+rgb_to_gray");
 
          if ((png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) != 0)
          {
@@ -1620,13 +1620,13 @@
                   case PNG_BACKGROUND_GAMMA_FILE:
                      g = png_reciprocal(png_ptr->colorspace.gamma);
                      gs = png_reciprocal2(png_ptr->colorspace.gamma,
-                        png_ptr->screen_gamma);
+                         png_ptr->screen_gamma);
                      break;
 
                   case PNG_BACKGROUND_GAMMA_UNIQUE:
                      g = png_reciprocal(png_ptr->background_gamma);
                      gs = png_reciprocal2(png_ptr->background_gamma,
-                        png_ptr->screen_gamma);
+                         png_ptr->screen_gamma);
                      break;
                   default:
                      g = PNG_FP_1;    /* back_1 */
@@ -1654,11 +1654,11 @@
                if (png_gamma_significant(g) != 0)
                {
                   back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
-                     g);
+                      g);
                   back_1.green = png_gamma_8bit_correct(
-                     png_ptr->background.green, g);
+                      png_ptr->background.green, g);
                   back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
-                     g);
+                      g);
                }
 
                else
@@ -1729,7 +1729,7 @@
                case PNG_BACKGROUND_GAMMA_FILE:
                   g = png_reciprocal(png_ptr->colorspace.gamma);
                   gs = png_reciprocal2(png_ptr->colorspace.gamma,
-                     png_ptr->screen_gamma);
+                      png_ptr->screen_gamma);
                   break;
 
                case PNG_BACKGROUND_GAMMA_UNIQUE:
@@ -4195,7 +4195,7 @@
  */
 static void
 png_do_expand_palette(png_row_infop row_info, png_bytep row,
-   png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
+    png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
 {
    int shift, value;
    png_bytep sp, dp;
@@ -4502,7 +4502,7 @@
             row_info->channels = 2;
             row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);
             row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
-               row_width);
+                row_width);
          }
       }
       else if (row_info->color_type == PNG_COLOR_TYPE_RGB &&
@@ -4762,7 +4762,7 @@
        (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
        row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
       png_do_strip_channel(row_info, png_ptr->row_buf + 1,
-         0 /* at_start == false, because SWAP_ALPHA happens later */);
+          0 /* at_start == false, because SWAP_ALPHA happens later */);
 #endif
 
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
diff --git a/pngrutil.c b/pngrutil.c
index c9747fc..1c8a179 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,8 +1,8 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.6.20 [December 3, 2014]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -90,7 +90,7 @@
 
    uval = (uval ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
    if ((uval & 0x80000000) == 0) /* no overflow */
-       return -(png_int_32)uval;
+      return -(png_int_32)uval;
    /* The following has to be safe; this function only gets called on PNG data
     * and if we get here that data is invalid.  0 is the most safe value and
     * if not then an attacker would surely just generate a PNG with 0 instead.
@@ -590,6 +590,7 @@
    }
 }
 
+#if defined(PNG_READ_zTXt_SUPPORTED) || defined (PNG_READ_iTXt_SUPPORTED)
 /*
  * Decompress trailing data in a chunk.  The assumption is that read_buffer
  * points at an allocated area holding the contents of a chunk with a
@@ -599,9 +600,9 @@
  */
 static int
 png_decompress_chunk(png_structrp png_ptr,
-   png_uint_32 chunklength, png_uint_32 prefix_size,
-   png_alloc_size_t *newlength /* must be initialized to the maximum! */,
-   int terminate /*add a '\0' to the end of the uncompressed data*/)
+    png_uint_32 chunklength, png_uint_32 prefix_size,
+    png_alloc_size_t *newlength /* must be initialized to the maximum! */,
+    int terminate /*add a '\0' to the end of the uncompressed data*/)
 {
    /* TODO: implement different limits for different types of chunk.
     *
@@ -638,8 +639,8 @@
          png_uint_32 lzsize = chunklength - prefix_size;
 
          ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
-            /* input: */ png_ptr->read_buffer + prefix_size, &lzsize,
-            /* output: */ NULL, newlength);
+             /* input: */ png_ptr->read_buffer + prefix_size, &lzsize,
+             /* output: */ NULL, newlength);
 
          if (ret == Z_STREAM_END)
          {
@@ -659,15 +660,15 @@
                 */
                png_alloc_size_t new_size = *newlength;
                png_alloc_size_t buffer_size = prefix_size + new_size +
-                  (terminate != 0);
+                   (terminate != 0);
                png_bytep text = png_voidcast(png_bytep, png_malloc_base(png_ptr,
-                  buffer_size));
+                   buffer_size));
 
                if (text != NULL)
                {
                   ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
-                     png_ptr->read_buffer + prefix_size, &lzsize,
-                     text + prefix_size, newlength);
+                      png_ptr->read_buffer + prefix_size, &lzsize,
+                      text + prefix_size, newlength);
 
                   if (ret == Z_STREAM_END)
                   {
@@ -754,6 +755,7 @@
       return Z_MEM_ERROR;
    }
 }
+#endif /* READ_zTXt || READ_iTXt */
 #endif /* READ_COMPRESSED_TEXT */
 
 #ifdef PNG_READ_iCCP_SUPPORTED
@@ -762,8 +764,8 @@
  */
 static int
 png_inflate_read(png_structrp png_ptr, png_bytep read_buffer, uInt read_size,
-   png_uint_32p chunk_bytes, png_bytep next_out, png_alloc_size_t *out_size,
-   int finish)
+    png_uint_32p chunk_bytes, png_bytep next_out, png_alloc_size_t *out_size,
+    int finish)
 {
    if (png_ptr->zowner == png_ptr->chunk_name)
    {
@@ -802,8 +804,8 @@
           * the available output is produced; this allows reading of truncated
           * streams.
           */
-         ret = PNG_INFLATE(png_ptr,
-            *chunk_bytes > 0 ? Z_NO_FLUSH : (finish ? Z_FINISH : Z_SYNC_FLUSH));
+         ret = PNG_INFLATE(png_ptr, *chunk_bytes > 0 ?
+             Z_NO_FLUSH : (finish ? Z_FINISH : Z_SYNC_FLUSH));
       }
       while (ret == Z_OK && (*out_size > 0 || png_ptr->zstream.avail_out > 0));
 
@@ -1292,7 +1294,7 @@
 
    png_ptr->colorspace.flags |= PNG_COLORSPACE_FROM_cHRM;
    (void)png_colorspace_set_chromaticities(png_ptr, &png_ptr->colorspace, &xy,
-      1/*prefer cHRM values*/);
+       1/*prefer cHRM values*/);
    png_colorspace_sync(png_ptr, info_ptr);
 }
 #endif
@@ -1432,8 +1434,8 @@
                png_ptr->zstream.next_in = (Bytef*)keyword + (keyword_length+2);
                png_ptr->zstream.avail_in = read_length;
                (void)png_inflate_read(png_ptr, local_buffer,
-                  (sizeof local_buffer), &length, profile_header, &size,
-                  0/*finish: don't, because the output is too small*/);
+                   (sizeof local_buffer), &length, profile_header, &size,
+                   0/*finish: don't, because the output is too small*/);
 
                if (size == 0)
                {
@@ -1443,14 +1445,14 @@
                      png_get_uint_32(profile_header);
 
                   if (png_icc_check_length(png_ptr, &png_ptr->colorspace,
-                     keyword, profile_length) != 0)
+                      keyword, profile_length) != 0)
                   {
                      /* The length is apparently ok, so we can check the 132
                       * byte header.
                       */
                      if (png_icc_check_header(png_ptr, &png_ptr->colorspace,
-                        keyword, profile_length, profile_header,
-                        png_ptr->color_type) != 0)
+                         keyword, profile_length, profile_header,
+                         png_ptr->color_type) != 0)
                      {
                         /* Now read the tag table; a variable size buffer is
                          * needed at this point, allocate one for the whole
@@ -1458,20 +1460,20 @@
                          * that none of these stuff will overflow.
                          */
                         const png_uint_32 tag_count = png_get_uint_32(
-                           profile_header+128);
+                            profile_header+128);
                         png_bytep profile = png_read_buffer(png_ptr,
-                           profile_length, 2/*silent*/);
+                            profile_length, 2/*silent*/);
 
                         if (profile != NULL)
                         {
                            memcpy(profile, profile_header,
-                              (sizeof profile_header));
+                               (sizeof profile_header));
 
                            size = 12 * tag_count;
 
                            (void)png_inflate_read(png_ptr, local_buffer,
-                              (sizeof local_buffer), &length,
-                              profile + (sizeof profile_header), &size, 0);
+                               (sizeof local_buffer), &length,
+                               profile + (sizeof profile_header), &size, 0);
 
                            /* Still expect a buffer error because we expect
                             * there to be some tag data!
@@ -1479,22 +1481,22 @@
                            if (size == 0)
                            {
                               if (png_icc_check_tag_table(png_ptr,
-                                 &png_ptr->colorspace, keyword, profile_length,
-                                 profile) != 0)
+                                  &png_ptr->colorspace, keyword, profile_length,
+                                  profile) != 0)
                               {
                                  /* The profile has been validated for basic
                                   * security issues, so read the whole thing in.
                                   */
                                  size = profile_length - (sizeof profile_header)
-                                    - 12 * tag_count;
+                                     - 12 * tag_count;
 
                                  (void)png_inflate_read(png_ptr, local_buffer,
-                                    (sizeof local_buffer), &length,
-                                    profile + (sizeof profile_header) +
-                                    12 * tag_count, &size, 1/*finish*/);
+                                     (sizeof local_buffer), &length,
+                                     profile + (sizeof profile_header) +
+                                     12 * tag_count, &size, 1/*finish*/);
 
                                  if (length > 0 && !(png_ptr->flags &
-                                       PNG_FLAG_BENIGN_ERRORS_WARN))
+                                     PNG_FLAG_BENIGN_ERRORS_WARN))
                                     errmsg = "extra compressed data";
 
                                  /* But otherwise allow extra data: */
@@ -1506,34 +1508,34 @@
                                         * keep going.
                                         */
                                        png_chunk_warning(png_ptr,
-                                          "extra compressed data");
+                                           "extra compressed data");
                                     }
 
                                     png_crc_finish(png_ptr, length);
                                     finished = 1;
 
-#                                   ifdef PNG_sRGB_SUPPORTED
+# if defined(PNG_sRGB_SUPPORTED) && PNG_sRGB_PROFILE_CHECKS >= 0
                                     /* Check for a match against sRGB */
                                     png_icc_set_sRGB(png_ptr,
-                                       &png_ptr->colorspace, profile,
-                                       png_ptr->zstream.adler);
-#                                   endif
+                                        &png_ptr->colorspace, profile,
+                                        png_ptr->zstream.adler);
+# endif
 
                                     /* Steal the profile for info_ptr. */
                                     if (info_ptr != NULL)
                                     {
                                        png_free_data(png_ptr, info_ptr,
-                                          PNG_FREE_ICCP, 0);
+                                           PNG_FREE_ICCP, 0);
 
                                        info_ptr->iccp_name = png_voidcast(char*,
-                                          png_malloc_base(png_ptr,
-                                          keyword_length+1));
+                                           png_malloc_base(png_ptr,
+                                           keyword_length+1));
                                        if (info_ptr->iccp_name != NULL)
                                        {
                                           memcpy(info_ptr->iccp_name, keyword,
-                                             keyword_length+1);
+                                              keyword_length+1);
                                           info_ptr->iccp_proflen =
-                                             profile_length;
+                                              profile_length;
                                           info_ptr->iccp_profile = profile;
                                           png_ptr->read_buffer = NULL; /*steal*/
                                           info_ptr->free_me |= PNG_FREE_ICCP;
@@ -2270,7 +2272,7 @@
    }
 
    png_set_pCAL(png_ptr, info_ptr, (png_charp)buffer, X0, X1, type, nparams,
-      (png_charp)units, params);
+       (png_charp)units, params);
 
    png_free(png_ptr, params);
 }
@@ -2313,7 +2315,7 @@
    }
 
    png_debug1(2, "Allocating and reading sCAL chunk data (%u bytes)",
-      length + 1);
+       length + 1);
 
    buffer = png_read_buffer(png_ptr, length+1, 2/*silent*/);
 
@@ -2365,7 +2367,7 @@
       else
          /* This is the (only) success case. */
          png_set_sCAL_s(png_ptr, info_ptr, buffer[0],
-            (png_charp)buffer+1, (png_charp)buffer+heighti);
+             (png_charp)buffer+1, (png_charp)buffer+heighti);
    }
 }
 #endif
@@ -2465,8 +2467,8 @@
 
    if (buffer == NULL)
    {
-     png_chunk_benign_error(png_ptr, "out of memory");
-     return;
+      png_chunk_benign_error(png_ptr, "out of memory");
+      return;
    }
 
    png_crc_read(png_ptr, buffer, length);
@@ -2573,7 +2575,7 @@
        * and text chunks.
        */
       if (png_decompress_chunk(png_ptr, length, keyword_length+2,
-         &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
+          &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
       {
          png_text text;
 
@@ -2713,7 +2715,7 @@
           * iCCP and text chunks.
           */
          if (png_decompress_chunk(png_ptr, length, prefix_length,
-            &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
+             &uncompressed_length, 1/*terminate*/) == Z_STREAM_END)
             buffer = png_ptr->read_buffer;
 
          else
@@ -2793,7 +2795,7 @@
       {
          /* Do a 'warn' here - it is handled below. */
          png_ptr->unknown_chunk.data = png_voidcast(png_bytep,
-            png_malloc_warn(png_ptr, length));
+             png_malloc_warn(png_ptr, length));
       }
    }
 
@@ -2818,7 +2820,7 @@
 /* Handle an unknown, or known but disabled, chunk */
 void /* PRIVATE */
 png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
-   png_uint_32 length, int keep)
+    png_uint_32 length, int keep)
 {
    int handled = 0; /* the chunk was handled */
 
@@ -2856,7 +2858,7 @@
       {
          /* Callback to user unknown chunk handler */
          int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
-            &png_ptr->unknown_chunk);
+             &png_ptr->unknown_chunk);
 
          /* ret is:
           * negative: An error occurred; png_chunk_error will be called.
@@ -2890,9 +2892,9 @@
                {
                   png_chunk_warning(png_ptr, "Saving unknown chunk:");
                   png_app_warning(png_ptr,
-                     "forcing save of an unhandled chunk;"
-                     " please call png_set_keep_unknown_chunks");
-                     /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
+                      "forcing save of an unhandled chunk;"
+                      " please call png_set_keep_unknown_chunks");
+                      /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
                }
 #              endif
                keep = PNG_HANDLE_CHUNK_IF_SAFE;
@@ -2985,7 +2987,7 @@
              * out; store the chunk.
              */
             png_set_unknown_chunks(png_ptr, info_ptr,
-               &png_ptr->unknown_chunk, 1);
+                &png_ptr->unknown_chunk, 1);
             handled = 1;
 #  ifdef PNG_USER_LIMITS_SUPPORTED
             break;
@@ -3418,8 +3420,8 @@
                   /* Everything is aligned for png_uint_16 copies, but try for
                    * png_uint_32 first.
                    */
-                  if (png_isaligned(dp, png_uint_32) != 0 &&
-                      png_isaligned(sp, png_uint_32) != 0 &&
+                  if (png_isaligned(dp, png_uint_32) &&
+                      png_isaligned(sp, png_uint_32) &&
                       bytes_to_copy % (sizeof (png_uint_32)) == 0 &&
                       bytes_to_jump % (sizeof (png_uint_32)) == 0)
                   {
@@ -3539,7 +3541,7 @@
 #ifdef PNG_READ_INTERLACING_SUPPORTED
 void /* PRIVATE */
 png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
-   png_uint_32 transformations /* Because these may affect the byte layout */)
+    png_uint_32 transformations /* Because these may affect the byte layout */)
 {
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
    /* Offset to next interlace block */
@@ -3783,7 +3785,7 @@
 
 static void
 png_read_filter_row_sub(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
+    png_const_bytep prev_row)
 {
    png_size_t i;
    png_size_t istop = row_info->rowbytes;
@@ -3801,7 +3803,7 @@
 
 static void
 png_read_filter_row_up(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
+    png_const_bytep prev_row)
 {
    png_size_t i;
    png_size_t istop = row_info->rowbytes;
@@ -3817,7 +3819,7 @@
 
 static void
 png_read_filter_row_avg(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
+    png_const_bytep prev_row)
 {
    png_size_t i;
    png_bytep rp = row;
@@ -3844,7 +3846,7 @@
 
 static void
 png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
+    png_const_bytep prev_row)
 {
    png_bytep rp_end = row + row_info->rowbytes;
    int a, c;
@@ -3892,7 +3894,7 @@
 
 static void
 png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row)
+    png_const_bytep prev_row)
 {
    int bpp = (row_info->pixel_depth + 7) >> 3;
    png_bytep rp_end = row + bpp;
@@ -3977,7 +3979,7 @@
 
 void /* PRIVATE */
 png_read_filter_row(png_structrp pp, png_row_infop row_info, png_bytep row,
-   png_const_bytep prev_row, int filter)
+    png_const_bytep prev_row, int filter)
 {
    /* OPTIMIZATION: DO NOT MODIFY THIS FUNCTION, instead #define
     * PNG_FILTER_OPTIMIZATIONS to a function that overrides the generic
@@ -3995,7 +3997,7 @@
 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
 void /* PRIVATE */
 png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
-   png_alloc_size_t avail_out)
+    png_alloc_size_t avail_out)
 {
    /* Loop reading IDATs and decompressing the result into output[avail_out] */
    png_ptr->zstream.next_out = output;
@@ -4447,42 +4449,42 @@
 
    if (row_bytes + 48 > png_ptr->old_big_row_buf_size)
    {
-     png_free(png_ptr, png_ptr->big_row_buf);
-     png_free(png_ptr, png_ptr->big_prev_row);
+      png_free(png_ptr, png_ptr->big_row_buf);
+      png_free(png_ptr, png_ptr->big_prev_row);
 
-     if (png_ptr->interlaced != 0)
-        png_ptr->big_row_buf = (png_bytep)png_calloc(png_ptr,
-            row_bytes + 48);
+      if (png_ptr->interlaced != 0)
+         png_ptr->big_row_buf = (png_bytep)png_calloc(png_ptr,
+             row_bytes + 48);
 
-     else
-        png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
+      else
+         png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
 
-     png_ptr->big_prev_row = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
+      png_ptr->big_prev_row = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
 
 #ifdef PNG_ALIGNED_MEMORY_SUPPORTED
-     /* Use 16-byte aligned memory for row_buf with at least 16 bytes
-      * of padding before and after row_buf; treat prev_row similarly.
-      * NOTE: the alignment is to the start of the pixels, one beyond the start
-      * of the buffer, because of the filter byte.  Prior to libpng 1.5.6 this
-      * was incorrect; the filter byte was aligned, which had the exact
-      * opposite effect of that intended.
-      */
-     {
-        png_bytep temp = png_ptr->big_row_buf + 32;
-        int extra = (int)((temp - (png_bytep)0) & 0x0f);
-        png_ptr->row_buf = temp - extra - 1/*filter byte*/;
+      /* Use 16-byte aligned memory for row_buf with at least 16 bytes
+       * of padding before and after row_buf; treat prev_row similarly.
+       * NOTE: the alignment is to the start of the pixels, one beyond the start
+       * of the buffer, because of the filter byte.  Prior to libpng 1.5.6 this
+       * was incorrect; the filter byte was aligned, which had the exact
+       * opposite effect of that intended.
+       */
+      {
+         png_bytep temp = png_ptr->big_row_buf + 32;
+         int extra = (int)((temp - (png_bytep)0) & 0x0f);
+         png_ptr->row_buf = temp - extra - 1/*filter byte*/;
 
-        temp = png_ptr->big_prev_row + 32;
-        extra = (int)((temp - (png_bytep)0) & 0x0f);
-        png_ptr->prev_row = temp - extra - 1/*filter byte*/;
-     }
+         temp = png_ptr->big_prev_row + 32;
+         extra = (int)((temp - (png_bytep)0) & 0x0f);
+         png_ptr->prev_row = temp - extra - 1/*filter byte*/;
+      }
 
 #else
-     /* Use 31 bytes of padding before and 17 bytes after row_buf. */
-     png_ptr->row_buf = png_ptr->big_row_buf + 31;
-     png_ptr->prev_row = png_ptr->big_prev_row + 31;
+      /* Use 31 bytes of padding before and 17 bytes after row_buf. */
+      png_ptr->row_buf = png_ptr->big_row_buf + 31;
+      png_ptr->prev_row = png_ptr->big_prev_row + 31;
 #endif
-     png_ptr->old_big_row_buf_size = row_bytes + 48;
+      png_ptr->old_big_row_buf_size = row_bytes + 48;
    }
 
 #ifdef PNG_MAX_MALLOC_64K
diff --git a/pngset.c b/pngset.c
index 43456b7..cccd9cd 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1,7 +1,7 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Last changed in libpng 1.6.23 [June 9, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 1998-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -104,14 +104,14 @@
     double green_x, double green_y, double blue_x, double blue_y)
 {
    png_set_cHRM_fixed(png_ptr, info_ptr,
-      png_fixed(png_ptr, white_x, "cHRM White X"),
-      png_fixed(png_ptr, white_y, "cHRM White Y"),
-      png_fixed(png_ptr, red_x, "cHRM Red X"),
-      png_fixed(png_ptr, red_y, "cHRM Red Y"),
-      png_fixed(png_ptr, green_x, "cHRM Green X"),
-      png_fixed(png_ptr, green_y, "cHRM Green Y"),
-      png_fixed(png_ptr, blue_x, "cHRM Blue X"),
-      png_fixed(png_ptr, blue_y, "cHRM Blue Y"));
+       png_fixed(png_ptr, white_x, "cHRM White X"),
+       png_fixed(png_ptr, white_y, "cHRM White Y"),
+       png_fixed(png_ptr, red_x, "cHRM Red X"),
+       png_fixed(png_ptr, red_y, "cHRM Red Y"),
+       png_fixed(png_ptr, green_x, "cHRM Green X"),
+       png_fixed(png_ptr, green_y, "cHRM Green Y"),
+       png_fixed(png_ptr, blue_x, "cHRM Blue X"),
+       png_fixed(png_ptr, blue_y, "cHRM Blue Y"));
 }
 
 void PNGAPI
@@ -120,15 +120,15 @@
     double blue_X, double blue_Y, double blue_Z)
 {
    png_set_cHRM_XYZ_fixed(png_ptr, info_ptr,
-      png_fixed(png_ptr, red_X, "cHRM Red X"),
-      png_fixed(png_ptr, red_Y, "cHRM Red Y"),
-      png_fixed(png_ptr, red_Z, "cHRM Red Z"),
-      png_fixed(png_ptr, green_X, "cHRM Green X"),
-      png_fixed(png_ptr, green_Y, "cHRM Green Y"),
-      png_fixed(png_ptr, green_Z, "cHRM Green Z"),
-      png_fixed(png_ptr, blue_X, "cHRM Blue X"),
-      png_fixed(png_ptr, blue_Y, "cHRM Blue Y"),
-      png_fixed(png_ptr, blue_Z, "cHRM Blue Z"));
+       png_fixed(png_ptr, red_X, "cHRM Red X"),
+       png_fixed(png_ptr, red_Y, "cHRM Red Y"),
+       png_fixed(png_ptr, red_Z, "cHRM Red Z"),
+       png_fixed(png_ptr, green_X, "cHRM Green X"),
+       png_fixed(png_ptr, green_Y, "cHRM Green Y"),
+       png_fixed(png_ptr, green_Z, "cHRM Green Z"),
+       png_fixed(png_ptr, blue_X, "cHRM Blue X"),
+       png_fixed(png_ptr, blue_Y, "cHRM Blue Y"),
+       png_fixed(png_ptr, blue_Z, "cHRM Blue Z"));
 }
 #  endif /* FLOATING_POINT */
 
@@ -316,10 +316,10 @@
 
    length = strlen(units) + 1;
    png_debug1(3, "allocating units for info (%lu bytes)",
-     (unsigned long)length);
+       (unsigned long)length);
 
    info_ptr->pcal_units = png_voidcast(png_charp,
-      png_malloc_warn(png_ptr, length));
+       png_malloc_warn(png_ptr, length));
 
    if (info_ptr->pcal_units == NULL)
    {
@@ -398,7 +398,7 @@
    png_debug1(3, "allocating unit for info (%u bytes)", (unsigned int)lengthw);
 
    info_ptr->scal_s_width = png_voidcast(png_charp,
-      png_malloc_warn(png_ptr, lengthw));
+       png_malloc_warn(png_ptr, lengthw));
 
    if (info_ptr->scal_s_width == NULL)
    {
@@ -414,7 +414,7 @@
    png_debug1(3, "allocating unit for info (%u bytes)", (unsigned int)lengthh);
 
    info_ptr->scal_s_height = png_voidcast(png_charp,
-      png_malloc_warn(png_ptr, lengthh));
+       png_malloc_warn(png_ptr, lengthh));
 
    if (info_ptr->scal_s_height == NULL)
    {
@@ -453,9 +453,9 @@
       char sheight[PNG_sCAL_MAX_DIGITS+1];
 
       png_ascii_from_fp(png_ptr, swidth, (sizeof swidth), width,
-         PNG_sCAL_PRECISION);
+          PNG_sCAL_PRECISION);
       png_ascii_from_fp(png_ptr, sheight, (sizeof sheight), height,
-         PNG_sCAL_PRECISION);
+          PNG_sCAL_PRECISION);
 
       png_set_sCAL_s(png_ptr, info_ptr, unit, swidth, sheight);
    }
@@ -648,7 +648,7 @@
     */
    {
       int result = png_colorspace_set_ICC(png_ptr, &info_ptr->colorspace, name,
-         proflen, profile, info_ptr->color_type);
+          proflen, profile, info_ptr->color_type);
 
       png_colorspace_sync_info(png_ptr, info_ptr);
 
@@ -673,7 +673,7 @@
 
    memcpy(new_iccp_name, name, length);
    new_iccp_profile = png_voidcast(png_bytep,
-      png_malloc_warn(png_ptr, proflen));
+       png_malloc_warn(png_ptr, proflen));
 
    if (new_iccp_profile == NULL)
    {
@@ -748,14 +748,14 @@
           * the overflow checks.
           */
          new_text = png_voidcast(png_textp,png_realloc_array(png_ptr,
-            info_ptr->text, old_num_text, max_text-old_num_text,
-            sizeof *new_text));
+             info_ptr->text, old_num_text, max_text-old_num_text,
+             sizeof *new_text));
       }
 
       if (new_text == NULL)
       {
          png_chunk_report(png_ptr, "too many text chunks",
-            PNG_CHUNK_WRITE_ERROR);
+             PNG_CHUNK_WRITE_ERROR);
 
          return 1;
       }
@@ -783,7 +783,7 @@
           text_ptr[i].compression >= PNG_TEXT_COMPRESSION_LAST)
       {
          png_chunk_report(png_ptr, "text compression mode is out of range",
-            PNG_CHUNK_WRITE_ERROR);
+             PNG_CHUNK_WRITE_ERROR);
          continue;
       }
 
@@ -815,7 +815,7 @@
 #  else /* iTXt */
       {
          png_chunk_report(png_ptr, "iTXt chunk not supported",
-            PNG_CHUNK_WRITE_ERROR);
+             PNG_CHUNK_WRITE_ERROR);
          continue;
       }
 #  endif
@@ -844,7 +844,7 @@
       if (textp->key == NULL)
       {
          png_chunk_report(png_ptr, "text chunk: out of memory",
-               PNG_CHUNK_WRITE_ERROR);
+             PNG_CHUNK_WRITE_ERROR);
 
          return 1;
       }
@@ -956,7 +956,7 @@
        {
          /* Changed from num_trans to PNG_MAX_PALETTE_LENGTH in version 1.2.1 */
           info_ptr->trans_alpha = png_voidcast(png_bytep,
-             png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH));
+              png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH));
           memcpy(info_ptr->trans_alpha, trans_alpha, (png_size_t)num_trans);
        }
        png_ptr->trans_alpha = info_ptr->trans_alpha;
@@ -976,7 +976,7 @@
              trans_color->green > sample_max ||
              trans_color->blue > sample_max)))
             png_warning(png_ptr,
-               "tRNS chunk has out-of-range samples for bit_depth");
+                "tRNS chunk has out-of-range samples for bit_depth");
       }
 #endif
 
@@ -1018,8 +1018,8 @@
     * overflows.  Notice that the parameters are (int) and (size_t)
     */
    np = png_voidcast(png_sPLT_tp,png_realloc_array(png_ptr,
-      info_ptr->splt_palettes, info_ptr->splt_palettes_num, nentries,
-      sizeof *np));
+       info_ptr->splt_palettes, info_ptr->splt_palettes_num, nentries,
+       sizeof *np));
 
    if (np == NULL)
    {
@@ -1080,7 +1080,7 @@
        * checked it when doing the allocation.
        */
       memcpy(np->entries, entries->entries,
-         entries->nentries * sizeof (png_sPLT_entry));
+          entries->nentries * sizeof (png_sPLT_entry));
 
       /* Note that 'continue' skips the advance of the out pointer and out
        * count, so an invalid entry is not added.
@@ -1110,10 +1110,10 @@
    {
       /* Write struct, so unknown chunks come from the app */
       png_app_warning(png_ptr,
-         "png_set_unknown_chunks now expects a valid location");
+          "png_set_unknown_chunks now expects a valid location");
       /* Use the old behavior */
       location = (png_byte)(png_ptr->mode &
-         (PNG_HAVE_IHDR|PNG_HAVE_PLTE|PNG_AFTER_IDAT));
+          (PNG_HAVE_IHDR|PNG_HAVE_PLTE|PNG_AFTER_IDAT));
    }
 
    /* This need not be an internal error - if the app calls
@@ -1136,7 +1136,7 @@
 
 void PNGAPI
 png_set_unknown_chunks(png_const_structrp png_ptr,
-   png_inforp info_ptr, png_const_unknown_chunkp unknowns, int num_unknowns)
+    png_inforp info_ptr, png_const_unknown_chunkp unknowns, int num_unknowns)
 {
    png_unknown_chunkp np;
 
@@ -1175,13 +1175,13 @@
     * appropriate to read or write.
     */
    np = png_voidcast(png_unknown_chunkp, png_realloc_array(png_ptr,
-         info_ptr->unknown_chunks, info_ptr->unknown_chunks_num, num_unknowns,
-         sizeof *np));
+       info_ptr->unknown_chunks, info_ptr->unknown_chunks_num, num_unknowns,
+       sizeof *np));
 
    if (np == NULL)
    {
       png_chunk_report(png_ptr, "too many unknown chunks",
-         PNG_CHUNK_WRITE_ERROR);
+          PNG_CHUNK_WRITE_ERROR);
 
       return;
    }
@@ -1210,12 +1210,12 @@
       else
       {
          np->data = png_voidcast(png_bytep,
-            png_malloc_base(png_ptr, unknowns->size));
+             png_malloc_base(png_ptr, unknowns->size));
 
          if (np->data == NULL)
          {
             png_chunk_report(png_ptr, "unknown chunk: out of memory",
-               PNG_CHUNK_WRITE_ERROR);
+                PNG_CHUNK_WRITE_ERROR);
             /* But just skip storing the unknown chunk */
             continue;
          }
@@ -1422,7 +1422,7 @@
       for (i=0; i<num_chunks; ++i)
       {
          old_num_chunks = add_one_chunk(new_list, old_num_chunks,
-            chunk_list+5*i, keep);
+             chunk_list+5*i, keep);
       }
 
       /* Now remove any spurious 'default' entries. */
@@ -1502,60 +1502,60 @@
 void PNGAPI
 png_set_compression_buffer_size(png_structrp png_ptr, png_size_t size)
 {
-    if (png_ptr == NULL)
-       return;
+   if (png_ptr == NULL)
+      return;
 
-    if (size == 0 || size > PNG_UINT_31_MAX)
-       png_error(png_ptr, "invalid compression buffer size");
+   if (size == 0 || size > PNG_UINT_31_MAX)
+      png_error(png_ptr, "invalid compression buffer size");
 
 #  ifdef PNG_SEQUENTIAL_READ_SUPPORTED
-      if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
-      {
-         png_ptr->IDAT_read_size = (png_uint_32)size; /* checked above */
-         return;
-      }
+   if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
+   {
+      png_ptr->IDAT_read_size = (png_uint_32)size; /* checked above */
+      return;
+   }
 #  endif
 
 #  ifdef PNG_WRITE_SUPPORTED
-      if ((png_ptr->mode & PNG_IS_READ_STRUCT) == 0)
+   if ((png_ptr->mode & PNG_IS_READ_STRUCT) == 0)
+   {
+      if (png_ptr->zowner != 0)
       {
-         if (png_ptr->zowner != 0)
-         {
-            png_warning(png_ptr,
-              "Compression buffer size cannot be changed because it is in use");
+         png_warning(png_ptr,
+             "Compression buffer size cannot be changed because it is in use");
 
-            return;
-         }
+         return;
+      }
 
 #ifndef __COVERITY__
-         /* Some compilers complain that this is always false.  However, it
-          * can be true when integer overflow happens.
-          */
-         if (size > ZLIB_IO_MAX)
-         {
-            png_warning(png_ptr,
-               "Compression buffer size limited to system maximum");
-            size = ZLIB_IO_MAX; /* must fit */
-         }
+      /* Some compilers complain that this is always false.  However, it
+       * can be true when integer overflow happens.
+       */
+      if (size > ZLIB_IO_MAX)
+      {
+         png_warning(png_ptr,
+             "Compression buffer size limited to system maximum");
+         size = ZLIB_IO_MAX; /* must fit */
+      }
 #endif
 
-         if (size < 6)
-         {
-            /* Deflate will potentially go into an infinite loop on a SYNC_FLUSH
-             * if this is permitted.
-             */
-            png_warning(png_ptr,
-               "Compression buffer size cannot be reduced below 6");
+      if (size < 6)
+      {
+         /* Deflate will potentially go into an infinite loop on a SYNC_FLUSH
+          * if this is permitted.
+          */
+         png_warning(png_ptr,
+             "Compression buffer size cannot be reduced below 6");
 
-            return;
-         }
-
-         if (png_ptr->zbuffer_size != size)
-         {
-            png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list);
-            png_ptr->zbuffer_size = (uInt)size;
-         }
+         return;
       }
+
+      if (png_ptr->zbuffer_size != size)
+      {
+         png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list);
+         png_ptr->zbuffer_size = (uInt)size;
+      }
+   }
 #  endif
 }
 
@@ -1662,7 +1662,9 @@
 png_uint_32 /* PRIVATE */
 png_check_keyword(png_structrp png_ptr, png_const_charp key, png_bytep new_key)
 {
+#ifdef PNG_WARNINGS_SUPPORTED
    png_const_charp orig_key = key;
+#endif
    png_uint_32 key_len = 0;
    int bad_character = 0;
    int space = 1;
@@ -1725,7 +1727,9 @@
 
       png_formatted_warning(png_ptr, p, "keyword \"@1\": bad character '0x@2'");
    }
-#endif /* WARNINGS */
+#else /* !WARNINGS */
+   PNG_UNUSED(png_ptr)
+#endif /* !WARNINGS */
 
    return key_len;
 }
diff --git a/pngstruct.h b/pngstruct.h
index c1f35ed..2b0eb49 100644
--- a/pngstruct.h
+++ b/pngstruct.h
@@ -1,8 +1,8 @@
 
 /* pngstruct.h - header file for PNG reference library
  *
- * Last changed in libpng 1.6.18 [July 23, 2015]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -249,7 +249,7 @@
    png_byte filter;           /* file filter type (always 0) */
    png_byte interlaced;       /* PNG_INTERLACE_NONE, PNG_INTERLACE_ADAM7 */
    png_byte pass;             /* current interlace pass (0 - 6) */
-   png_byte do_filter;        /* row filter flags (see PNG_FILTER_ below ) */
+   png_byte do_filter;        /* row filter flags (see PNG_FILTER_ in png.h ) */
    png_byte color_type;       /* color type of file */
    png_byte bit_depth;        /* bit depth of file */
    png_byte usr_bit_depth;    /* bit depth of users row: write only */
diff --git a/pngtest.c b/pngtest.c
index 37e2209..dd222a6 100644
--- a/pngtest.c
+++ b/pngtest.c
@@ -1,8 +1,8 @@
 
 /* pngtest.c - a simple test program to test libpng
  *
- * Last changed in libpng 1.5.25 [December 3, 2015]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -139,13 +139,13 @@
 static int
 tIME_to_str(png_structp png_ptr, png_charp ts, png_const_timep t)
 {
-    png_const_charp str = png_convert_to_rfc1123(png_ptr, t);
+   png_const_charp str = png_convert_to_rfc1123(png_ptr, t);
 
-    if (str == NULL)
-        return 0;
+   if (str == NULL)
+       return 0;
 
-    strcpy(ts, str);
-    return 1;
+   strcpy(ts, str);
+   return 1;
 }
 #endif /* older libpng */
 #endif
@@ -249,95 +249,95 @@
     *  png_byte pixel_depth   bits per pixel (depth*channels)
     */
 
-    /* Counts the number of zero samples (or zero pixels if color_type is 3 */
+   /* Counts the number of zero samples (or zero pixels if color_type is 3 */
 
-    if (row_info->color_type == 0 || row_info->color_type == 3)
-    {
-       int pos = 0;
-       png_uint_32 n, nstop;
+   if (row_info->color_type == 0 || row_info->color_type == 3)
+   {
+      int pos = 0;
+      png_uint_32 n, nstop;
 
-       for (n = 0, nstop=row_info->width; n<nstop; n++)
-       {
-          if (row_info->bit_depth == 1)
-          {
-             if (((*dp << pos++ ) & 0x80) == 0)
-                zero_samples++;
+      for (n = 0, nstop=row_info->width; n<nstop; n++)
+      {
+         if (row_info->bit_depth == 1)
+         {
+            if (((*dp << pos++ ) & 0x80) == 0)
+               zero_samples++;
 
-             if (pos == 8)
-             {
-                pos = 0;
-                dp++;
-             }
-          }
+            if (pos == 8)
+            {
+               pos = 0;
+               dp++;
+            }
+         }
 
-          if (row_info->bit_depth == 2)
-          {
-             if (((*dp << (pos+=2)) & 0xc0) == 0)
-                zero_samples++;
+         if (row_info->bit_depth == 2)
+         {
+            if (((*dp << (pos+=2)) & 0xc0) == 0)
+               zero_samples++;
 
-             if (pos == 8)
-             {
-                pos = 0;
-                dp++;
-             }
-          }
+            if (pos == 8)
+            {
+               pos = 0;
+               dp++;
+            }
+         }
 
-          if (row_info->bit_depth == 4)
-          {
-             if (((*dp << (pos+=4)) & 0xf0) == 0)
-                zero_samples++;
+         if (row_info->bit_depth == 4)
+         {
+            if (((*dp << (pos+=4)) & 0xf0) == 0)
+               zero_samples++;
 
-             if (pos == 8)
-             {
-                pos = 0;
-                dp++;
-             }
-          }
+            if (pos == 8)
+            {
+               pos = 0;
+               dp++;
+            }
+         }
 
-          if (row_info->bit_depth == 8)
-             if (*dp++ == 0)
-                zero_samples++;
+         if (row_info->bit_depth == 8)
+            if (*dp++ == 0)
+               zero_samples++;
 
-          if (row_info->bit_depth == 16)
-          {
-             if ((*dp | *(dp+1)) == 0)
-                zero_samples++;
-             dp+=2;
-          }
-       }
-    }
-    else /* Other color types */
-    {
-       png_uint_32 n, nstop;
-       int channel;
-       int color_channels = row_info->channels;
-       if (row_info->color_type > 3)
-          color_channels--;
+         if (row_info->bit_depth == 16)
+         {
+            if ((*dp | *(dp+1)) == 0)
+               zero_samples++;
+            dp+=2;
+         }
+      }
+   }
+   else /* Other color types */
+   {
+      png_uint_32 n, nstop;
+      int channel;
+      int color_channels = row_info->channels;
+      if (row_info->color_type > 3)
+         color_channels--;
 
-       for (n = 0, nstop=row_info->width; n<nstop; n++)
-       {
-          for (channel = 0; channel < color_channels; channel++)
-          {
-             if (row_info->bit_depth == 8)
-                if (*dp++ == 0)
-                   zero_samples++;
+      for (n = 0, nstop=row_info->width; n<nstop; n++)
+      {
+         for (channel = 0; channel < color_channels; channel++)
+         {
+            if (row_info->bit_depth == 8)
+               if (*dp++ == 0)
+                  zero_samples++;
 
-             if (row_info->bit_depth == 16)
-             {
-                if ((*dp | *(dp+1)) == 0)
-                   zero_samples++;
+            if (row_info->bit_depth == 16)
+            {
+               if ((*dp | *(dp+1)) == 0)
+                  zero_samples++;
 
-                dp+=2;
-             }
-          }
-          if (row_info->color_type > 3)
-          {
-             dp++;
-             if (row_info->bit_depth == 16)
-                dp++;
-          }
-       }
-    }
+               dp+=2;
+            }
+         }
+         if (row_info->color_type > 3)
+         {
+            dp++;
+            if (row_info->bit_depth == 16)
+               dp++;
+         }
+      }
+   }
 }
 #endif /* WRITE_USER_TRANSFORM */
 
@@ -354,10 +354,10 @@
 #ifdef PNG_IO_STATE_SUPPORTED
 void
 pngtest_check_io_state(png_structp png_ptr, png_size_t data_length,
-   png_uint_32 io_op);
+    png_uint_32 io_op);
 void
 pngtest_check_io_state(png_structp png_ptr, png_size_t data_length,
-   png_uint_32 io_op)
+    png_uint_32 io_op)
 {
    png_uint_32 io_state = png_get_io_state(png_ptr);
    int err = 0;
@@ -541,7 +541,7 @@
       memory_infop pinfo;
       png_set_mem_fn(png_ptr, NULL, NULL, NULL);
       pinfo = (memory_infop)png_malloc(png_ptr,
-         (sizeof *pinfo));
+          (sizeof *pinfo));
       pinfo->size = size;
       current_allocation += size;
       total_allocation += size;
@@ -571,7 +571,7 @@
 
       if (verbose != 0)
          printf("png_malloc %lu bytes at %p\n", (unsigned long)size,
-            pinfo->pointer);
+             pinfo->pointer);
 
       return (png_voidp)(pinfo->pointer);
    }
@@ -778,9 +778,9 @@
 
    if (verbose != 0)
       fprintf(STDERR, " vpAg = %lu x %lu, units = %d\n",
-        (unsigned long)user_chunk_data.vpAg_width,
-        (unsigned long)user_chunk_data.vpAg_height,
-        user_chunk_data.vpAg_units);
+          (unsigned long)user_chunk_data.vpAg_width,
+          (unsigned long)user_chunk_data.vpAg_height,
+          user_chunk_data.vpAg_units);
 
    png_save_uint_32(vpag_chunk_data, user_chunk_data.vpAg_width);
    png_save_uint_32(vpag_chunk_data + 4, user_chunk_data.vpAg_height);
@@ -821,7 +821,7 @@
 #ifdef PNG_TEXT_SUPPORTED
 static void
 pngtest_check_text_support(png_structp png_ptr, png_textp text_ptr,
-   int num_text)
+    int num_text)
 {
    while (num_text > 0)
    {
@@ -903,26 +903,26 @@
    pngtest_debug("Allocating read and write structures");
 #if defined(PNG_USER_MEM_SUPPORTED) && PNG_DEBUG
    read_ptr =
-      png_create_read_struct_2(PNG_LIBPNG_VER_STRING, NULL,
-      NULL, NULL, NULL, png_debug_malloc, png_debug_free);
+       png_create_read_struct_2(PNG_LIBPNG_VER_STRING, NULL,
+       NULL, NULL, NULL, png_debug_malloc, png_debug_free);
 #else
    read_ptr =
-      png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+       png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
 #endif
    png_set_error_fn(read_ptr, &error_parameters, pngtest_error,
-      pngtest_warning);
+       pngtest_warning);
 
 #ifdef PNG_WRITE_SUPPORTED
 #if defined(PNG_USER_MEM_SUPPORTED) && PNG_DEBUG
    write_ptr =
-      png_create_write_struct_2(PNG_LIBPNG_VER_STRING, NULL,
-      NULL, NULL, NULL, png_debug_malloc, png_debug_free);
+       png_create_write_struct_2(PNG_LIBPNG_VER_STRING, NULL,
+       NULL, NULL, NULL, png_debug_malloc, png_debug_free);
 #else
    write_ptr =
-      png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+       png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
 #endif
    png_set_error_fn(write_ptr, &error_parameters, pngtest_error,
-      pngtest_warning);
+       pngtest_warning);
 #endif
    pngtest_debug("Allocating read_info, write_info and end_info structures");
    read_info_ptr = png_create_info_struct(read_ptr);
@@ -935,7 +935,7 @@
 #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
    init_callback_info(read_info_ptr);
    png_set_read_user_chunk_fn(read_ptr, &user_chunk_data,
-     read_user_chunk_callback);
+       read_user_chunk_callback);
 #endif
 
 #ifdef PNG_SETJMP_SUPPORTED
@@ -1010,9 +1010,9 @@
 #  ifdef PNG_WRITE_SUPPORTED
    png_set_write_fn(write_ptr, (png_voidp)fpout,  pngtest_write_data,
 #    ifdef PNG_WRITE_FLUSH_SUPPORTED
-      pngtest_flush);
+       pngtest_flush);
 #    else
-      NULL);
+       NULL);
 #    endif
 #  endif
 #endif
@@ -1052,11 +1052,11 @@
     */
 #ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
    png_set_keep_unknown_chunks(read_ptr, PNG_HANDLE_CHUNK_ALWAYS,
-      NULL, 0);
+       NULL, 0);
 #endif
 #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
    png_set_keep_unknown_chunks(write_ptr, PNG_HANDLE_CHUNK_ALWAYS,
-      NULL, 0);
+       NULL, 0);
 #endif
 #endif
 
@@ -1080,7 +1080,7 @@
           &color_type, &interlace_type, &compression_type, &filter_type) != 0)
       {
          png_set_IHDR(write_ptr, write_info_ptr, width, height, bit_depth,
-            color_type, interlace_type, compression_type, filter_type);
+             color_type, interlace_type, compression_type, filter_type);
          /* num_passes may not be available below if interlace support is not
           * provided by libpng for both read and write.
           */
@@ -1107,13 +1107,13 @@
 #ifdef PNG_cHRM_SUPPORTED
    {
       png_fixed_point white_x, white_y, red_x, red_y, green_x, green_y, blue_x,
-         blue_y;
+          blue_y;
 
       if (png_get_cHRM_fixed(read_ptr, read_info_ptr, &white_x, &white_y,
-         &red_x, &red_y, &green_x, &green_y, &blue_x, &blue_y) != 0)
+          &red_x, &red_y, &green_x, &green_y, &blue_x, &blue_y) != 0)
       {
          png_set_cHRM_fixed(write_ptr, write_info_ptr, white_x, white_y, red_x,
-            red_y, green_x, green_y, blue_x, blue_y);
+             red_y, green_x, green_y, blue_x, blue_y);
       }
    }
 #endif
@@ -1130,13 +1130,13 @@
 #ifdef PNG_cHRM_SUPPORTED
    {
       double white_x, white_y, red_x, red_y, green_x, green_y, blue_x,
-         blue_y;
+          blue_y;
 
       if (png_get_cHRM(read_ptr, read_info_ptr, &white_x, &white_y, &red_x,
-         &red_y, &green_x, &green_y, &blue_x, &blue_y) != 0)
+          &red_y, &green_x, &green_y, &blue_x, &blue_y) != 0)
       {
          png_set_cHRM(write_ptr, write_info_ptr, white_x, white_y, red_x,
-            red_y, green_x, green_y, blue_x, blue_y);
+             red_y, green_x, green_y, blue_x, blue_y);
       }
    }
 #endif
@@ -1158,10 +1158,10 @@
       int compression_type;
 
       if (png_get_iCCP(read_ptr, read_info_ptr, &name, &compression_type,
-                      &profile, &proflen) != 0)
+          &profile, &proflen) != 0)
       {
          png_set_iCCP(write_ptr, write_info_ptr, name, compression_type,
-                      profile, proflen);
+             profile, proflen);
       }
    }
 #endif
@@ -1218,10 +1218,10 @@
       int type, nparams;
 
       if (png_get_pCAL(read_ptr, read_info_ptr, &purpose, &X0, &X1, &type,
-         &nparams, &units, &params) != 0)
+          &nparams, &units, &params) != 0)
       {
          png_set_pCAL(write_ptr, write_info_ptr, purpose, X0, X1, type,
-            nparams, units, params);
+             nparams, units, params);
       }
    }
 #endif
@@ -1251,7 +1251,7 @@
       double scal_width, scal_height;
 
       if (png_get_sCAL(read_ptr, read_info_ptr, &unit, &scal_width,
-         &scal_height) != 0)
+          &scal_height) != 0)
       {
          png_set_sCAL(write_ptr, write_info_ptr, unit, scal_width, scal_height);
       }
@@ -1263,7 +1263,7 @@
       png_charp scal_width, scal_height;
 
       if (png_get_sCAL_s(read_ptr, read_info_ptr, &unit, &scal_width,
-          &scal_height) != 0)
+           &scal_height) != 0)
       {
          png_set_sCAL_s(write_ptr, write_info_ptr, unit, scal_width,
              scal_height);
@@ -1304,7 +1304,7 @@
             for (i=0; i<num_text; i++)
             {
                printf("   Text compression[%d]=%d\n",
-                     i, text_ptr[i].compression);
+                   i, text_ptr[i].compression);
             }
          }
 
@@ -1341,7 +1341,7 @@
       png_color_16p trans_color;
 
       if (png_get_tRNS(read_ptr, read_info_ptr, &trans_alpha, &num_trans,
-         &trans_color) != 0)
+          &trans_color) != 0)
       {
          int sample_max = (1 << bit_depth);
          /* libpng doesn't reject a tRNS chunk with out-of-range samples */
@@ -1360,12 +1360,12 @@
    {
       png_unknown_chunkp unknowns;
       int num_unknowns = png_get_unknown_chunks(read_ptr, read_info_ptr,
-         &unknowns);
+          &unknowns);
 
       if (num_unknowns != 0)
       {
          png_set_unknown_chunks(write_ptr, write_info_ptr, unknowns,
-           num_unknowns);
+             num_unknowns);
 #if PNG_LIBPNG_VER < 10600
          /* Copy the locations from the read_info_ptr.  The automatically
           * generated locations in write_end_info_ptr are wrong prior to 1.6.0
@@ -1375,7 +1375,7 @@
             int i;
             for (i = 0; i < num_unknowns; i++)
               png_set_unknown_chunk_location(write_ptr, write_info_ptr, i,
-                unknowns[i].location);
+                  unknowns[i].location);
          }
 #endif
       }
@@ -1400,7 +1400,7 @@
 #ifdef SINGLE_ROWBUF_ALLOC
    pngtest_debug("Allocating row buffer...");
    row_buf = (png_bytep)png_malloc(read_ptr,
-      png_get_rowbytes(read_ptr, read_info_ptr));
+       png_get_rowbytes(read_ptr, read_info_ptr));
 
    pngtest_debug1("\t0x%08lx", (unsigned long)row_buf);
 #endif /* SINGLE_ROWBUF_ALLOC */
@@ -1414,10 +1414,10 @@
     */
    if (png_set_interlace_handling(read_ptr) != num_passes)
       png_error(write_ptr,
-            "png_set_interlace_handling(read): wrong pass count ");
+          "png_set_interlace_handling(read): wrong pass count ");
    if (png_set_interlace_handling(write_ptr) != num_passes)
       png_error(write_ptr,
-            "png_set_interlace_handling(write): wrong pass count ");
+          "png_set_interlace_handling(write): wrong pass count ");
 #else /* png_set_interlace_handling not called on either read or write */
 #  define calc_pass_height
 #endif /* not using libpng interlace handling */
@@ -1454,10 +1454,10 @@
          pngtest_debug2("Allocating row buffer (pass %d, y = %u)...", pass, y);
 
          row_buf = (png_bytep)png_malloc(read_ptr,
-            png_get_rowbytes(read_ptr, read_info_ptr));
+             png_get_rowbytes(read_ptr, read_info_ptr));
 
          pngtest_debug2("\t0x%08lx (%lu bytes)", (unsigned long)row_buf,
-            (unsigned long)png_get_rowbytes(read_ptr, read_info_ptr));
+             (unsigned long)png_get_rowbytes(read_ptr, read_info_ptr));
 
 #endif /* !SINGLE_ROWBUF_ALLOC */
          png_read_rows(read_ptr, (png_bytepp)&row_buf, NULL, 1);
@@ -1515,7 +1515,7 @@
             for (i=0; i<num_text; i++)
             {
                printf("   Text compression[%d]=%d\n",
-                     i, text_ptr[i].compression);
+                   i, text_ptr[i].compression);
             }
          }
 
@@ -1549,12 +1549,12 @@
    {
       png_unknown_chunkp unknowns;
       int num_unknowns = png_get_unknown_chunks(read_ptr, end_info_ptr,
-         &unknowns);
+          &unknowns);
 
       if (num_unknowns != 0)
       {
          png_set_unknown_chunks(write_ptr, write_end_info_ptr, unknowns,
-           num_unknowns);
+             num_unknowns);
 #if PNG_LIBPNG_VER < 10600
          /* Copy the locations from the read_info_ptr.  The automatically
           * generated locations in write_end_info_ptr are wrong prior to 1.6.0
@@ -1564,7 +1564,7 @@
             int i;
             for (i = 0; i < num_unknowns; i++)
               png_set_unknown_chunk_location(write_ptr, write_end_info_ptr, i,
-                unknowns[i].location);
+                  unknowns[i].location);
          }
 #endif
       }
@@ -1598,7 +1598,7 @@
       iwidth = png_get_image_width(write_ptr, write_info_ptr);
       iheight = png_get_image_height(write_ptr, write_info_ptr);
       fprintf(STDERR, "\n Image width = %lu, height = %lu\n",
-         (unsigned long)iwidth, (unsigned long)iheight);
+          (unsigned long)iwidth, (unsigned long)iheight);
    }
 #endif
 
@@ -1631,7 +1631,7 @@
        * above, but this is safe.
        */
       fprintf(STDERR, "\n  %s: %d libpng errors found (%d warnings)",
-         inname, error_count, warning_count);
+          inname, error_count, warning_count);
 
       if (strict != 0)
          return (1);
@@ -1642,14 +1642,14 @@
       else if (unsupported_chunks > 0)
       {
          fprintf(STDERR, "\n  %s: unsupported chunks (%d)%s",
-            inname, unsupported_chunks, strict ? ": IGNORED --strict!" : "");
+             inname, unsupported_chunks, strict ? ": IGNORED --strict!" : "");
       }
 #  endif
 
    else if (warning_count > 0)
    {
       fprintf(STDERR, "\n  %s: %d libpng warnings found",
-         inname, warning_count);
+          inname, warning_count);
 
       if (strict != 0)
          return (1);
@@ -1685,18 +1685,19 @@
          if (num_in != num_out)
          {
             fprintf(STDERR, "\nFiles %s and %s are of a different size\n",
-                    inname, outname);
+                inname, outname);
 
             if (wrote_question == 0 && unsupported_chunks == 0)
             {
                fprintf(STDERR,
-         "   Was %s written with the same maximum IDAT chunk size (%d bytes),",
-                 inname, PNG_ZBUF_SIZE);
+                   "   Was %s written with the same maximum IDAT"
+                   " chunk size (%d bytes),",
+                   inname, PNG_ZBUF_SIZE);
                fprintf(STDERR,
-                 "\n   filtering heuristic (libpng default), compression");
+                   "\n   filtering heuristic (libpng default), compression");
                fprintf(STDERR,
-                 " level (zlib default),\n   and zlib version (%s)?\n\n",
-                 ZLIB_VERSION);
+                   " level (zlib default),\n   and zlib version (%s)?\n\n",
+                   ZLIB_VERSION);
                wrote_question = 1;
             }
 
@@ -1716,17 +1717,18 @@
          if (memcmp(inbuf, outbuf, num_in))
          {
             fprintf(STDERR, "\nFiles %s and %s are different\n", inname,
-               outname);
+                outname);
 
             if (wrote_question == 0 && unsupported_chunks == 0)
             {
                fprintf(STDERR,
-         "   Was %s written with the same maximum IDAT chunk size (%d bytes),",
+                   "   Was %s written with the same maximum"
+                   " IDAT chunk size (%d bytes),",
                     inname, PNG_ZBUF_SIZE);
                fprintf(STDERR,
-                 "\n   filtering heuristic (libpng default), compression");
+                   "\n   filtering heuristic (libpng default), compression");
                fprintf(STDERR,
-                 " level (zlib default),\n   and zlib version (%s)?\n\n",
+                   " level (zlib default),\n   and zlib version (%s)?\n\n",
                  ZLIB_VERSION);
                wrote_question = 1;
             }
@@ -1777,12 +1779,12 @@
    fprintf(STDERR, "%s", png_get_copyright(NULL));
    /* Show the version of libpng used in building the library */
    fprintf(STDERR, " library (%lu):%s",
-      (unsigned long)png_access_version_number(),
-      png_get_header_version(NULL));
+       (unsigned long)png_access_version_number(),
+       png_get_header_version(NULL));
 
    /* Show the version of libpng used in building the application */
    fprintf(STDERR, " pngtest (%lu):%s", (unsigned long)PNG_LIBPNG_VER,
-      PNG_HEADER_VERSION_STRING);
+       PNG_HEADER_VERSION_STRING);
 
    /* Do some consistency checking on the memory allocation settings, I'm
     * not sure this matters, but it is nice to know, the first of these
@@ -1800,7 +1802,7 @@
    if (strcmp(png_libpng_ver, PNG_LIBPNG_VER_STRING))
    {
       fprintf(STDERR,
-         "Warning: versions are different between png.h and png.c\n");
+          "Warning: versions are different between png.h and png.c\n");
       fprintf(STDERR, "  png.h version: %s\n", PNG_LIBPNG_VER_STRING);
       fprintf(STDERR, "  png.c version: %s\n\n", png_libpng_ver);
       ++ierror;
@@ -1855,19 +1857,19 @@
    }
 
    if (multiple == 0 && argc == 3 + verbose)
-     outname = argv[2 + verbose];
+      outname = argv[2 + verbose];
 
    if ((multiple == 0 && argc > 3 + verbose) ||
        (multiple != 0 && argc < 2))
    {
-     fprintf(STDERR,
-       "usage: %s [infile.png] [outfile.png]\n\t%s -m {infile.png}\n",
-        argv[0], argv[0]);
-     fprintf(STDERR,
-       "  reads/writes one PNG file (without -m) or multiple files (-m)\n");
-     fprintf(STDERR,
-       "  with -m %s is used as a temporary file\n", outname);
-     exit(1);
+      fprintf(STDERR,
+          "usage: %s [infile.png] [outfile.png]\n\t%s -m {infile.png}\n",
+          argv[0], argv[0]);
+      fprintf(STDERR,
+          "  reads/writes one PNG file (without -m) or multiple files (-m)\n");
+      fprintf(STDERR,
+          "  with -m %s is used as a temporary file\n", outname);
+      exit(1);
    }
 
    if (multiple != 0)
@@ -1888,7 +1890,7 @@
          {
 #ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
             fprintf(STDERR, "\n PASS (%lu zero samples)\n",
-               (unsigned long)zero_samples);
+                (unsigned long)zero_samples);
 #else
             fprintf(STDERR, " PASS\n");
 #endif
@@ -1908,20 +1910,20 @@
 #if defined(PNG_USER_MEM_SUPPORTED) && PNG_DEBUG
          if (allocation_now != current_allocation)
             fprintf(STDERR, "MEMORY ERROR: %d bytes lost\n",
-               current_allocation - allocation_now);
+                current_allocation - allocation_now);
 
          if (current_allocation != 0)
          {
             memory_infop pinfo = pinformation;
 
             fprintf(STDERR, "MEMORY ERROR: %d bytes still allocated\n",
-               current_allocation);
+                current_allocation);
 
             while (pinfo != NULL)
             {
                fprintf(STDERR, " %lu bytes at %p\n",
-                 (unsigned long)pinfo->size,
-                 pinfo->pointer);
+                   (unsigned long)pinfo->size,
+                   pinfo->pointer);
                pinfo = pinfo->next;
             }
          }
@@ -1929,13 +1931,13 @@
       }
 #if defined(PNG_USER_MEM_SUPPORTED) && PNG_DEBUG
          fprintf(STDERR, " Current memory allocation: %10d bytes\n",
-            current_allocation);
+             current_allocation);
          fprintf(STDERR, " Maximum memory allocation: %10d bytes\n",
-            maximum_allocation);
+             maximum_allocation);
          fprintf(STDERR, " Total   memory allocation: %10d bytes\n",
-            total_allocation);
+             total_allocation);
          fprintf(STDERR, "     Number of allocations: %10d\n",
-            num_allocations);
+             num_allocations);
 #endif
    }
 
@@ -1970,7 +1972,7 @@
             {
 #ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
                 fprintf(STDERR, "\n PASS (%lu zero samples)\n",
-                   (unsigned long)zero_samples);
+                    (unsigned long)zero_samples);
 #else
                 fprintf(STDERR, " PASS\n");
 #endif
@@ -1997,19 +1999,19 @@
 #if defined(PNG_USER_MEM_SUPPORTED) && PNG_DEBUG
          if (allocation_now != current_allocation)
              fprintf(STDERR, "MEMORY ERROR: %d bytes lost\n",
-               current_allocation - allocation_now);
+                 current_allocation - allocation_now);
 
          if (current_allocation != 0)
          {
              memory_infop pinfo = pinformation;
 
              fprintf(STDERR, "MEMORY ERROR: %d bytes still allocated\n",
-                current_allocation);
+                 current_allocation);
 
              while (pinfo != NULL)
              {
                 fprintf(STDERR, " %lu bytes at %p\n",
-                   (unsigned long)pinfo->size, pinfo->pointer);
+                    (unsigned long)pinfo->size, pinfo->pointer);
                 pinfo = pinfo->next;
              }
           }
@@ -2017,13 +2019,13 @@
        }
 #if defined(PNG_USER_MEM_SUPPORTED) && PNG_DEBUG
        fprintf(STDERR, " Current memory allocation: %10d bytes\n",
-          current_allocation);
+           current_allocation);
        fprintf(STDERR, " Maximum memory allocation: %10d bytes\n",
-          maximum_allocation);
+           maximum_allocation);
        fprintf(STDERR, " Total   memory allocation: %10d bytes\n",
-          total_allocation);
+           total_allocation);
        fprintf(STDERR, "     Number of allocations: %10d\n",
-            num_allocations);
+           num_allocations);
 #endif
    }
 
@@ -2032,13 +2034,13 @@
    t_misc += (t_stop - t_start);
    t_start = t_stop;
    fprintf(STDERR, " CPU time used = %.3f seconds",
-      (t_misc+t_decode+t_encode)/(float)CLOCKS_PER_SEC);
+       (t_misc+t_decode+t_encode)/(float)CLOCKS_PER_SEC);
    fprintf(STDERR, " (decoding %.3f,\n",
-      t_decode/(float)CLOCKS_PER_SEC);
+       t_decode/(float)CLOCKS_PER_SEC);
    fprintf(STDERR, "        encoding %.3f ,",
-      t_encode/(float)CLOCKS_PER_SEC);
+       t_encode/(float)CLOCKS_PER_SEC);
    fprintf(STDERR, " other %.3f seconds)\n\n",
-      t_misc/(float)CLOCKS_PER_SEC);
+       t_misc/(float)CLOCKS_PER_SEC);
 #endif
 
    if (ierror == 0)
@@ -2050,19 +2052,19 @@
    dummy_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    fprintf(STDERR, " Default limits:\n");
    fprintf(STDERR, "  width_max  = %lu\n",
-      (unsigned long) png_get_user_width_max(dummy_ptr));
+       (unsigned long) png_get_user_width_max(dummy_ptr));
    fprintf(STDERR, "  height_max = %lu\n",
-      (unsigned long) png_get_user_height_max(dummy_ptr));
+       (unsigned long) png_get_user_height_max(dummy_ptr));
    if (png_get_chunk_cache_max(dummy_ptr) == 0)
       fprintf(STDERR, "  cache_max  = unlimited\n");
    else
       fprintf(STDERR, "  cache_max  = %lu\n",
-         (unsigned long) png_get_chunk_cache_max(dummy_ptr));
+          (unsigned long) png_get_chunk_cache_max(dummy_ptr));
    if (png_get_chunk_malloc_max(dummy_ptr) == 0)
       fprintf(STDERR, "  malloc_max = unlimited\n");
    else
       fprintf(STDERR, "  malloc_max = %lu\n",
-         (unsigned long) png_get_chunk_malloc_max(dummy_ptr));
+          (unsigned long) png_get_chunk_malloc_max(dummy_ptr));
    png_destroy_read_struct(&dummy_ptr, NULL, NULL);
 
    return (int)(ierror != 0);
@@ -2072,11 +2074,11 @@
 main(void)
 {
    fprintf(STDERR,
-      " test ignored because libpng was not built with read support\n");
+       " test ignored because libpng was not built with read support\n");
    /* And skip this test */
    return SKIP;
 }
 #endif
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_23 Your_png_h_is_not_version_1_6_23;
+typedef png_libpng_version_1_6_24 Your_png_h_is_not_version_1_6_24;
diff --git a/pngtrans.c b/pngtrans.c
index 7f8cc45..e5cbd79 100644
--- a/pngtrans.c
+++ b/pngtrans.c
@@ -1,8 +1,8 @@
 
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  *
- * Last changed in libpng 1.6.18 [July 23, 2015]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -172,13 +172,14 @@
                    * size!
                    */
                   png_app_error(png_ptr,
-                     "png_set_filler is invalid for low bit depth gray output");
+                      "png_set_filler is invalid for"
+                      " low bit depth gray output");
                   return;
                }
 
             default:
                png_app_error(png_ptr,
-                  "png_set_filler: inappropriate color type");
+                   "png_set_filler: inappropriate color type");
                return;
          }
 #     else
@@ -797,7 +798,7 @@
       (png_ptr->flags & PNG_FLAG_ROW_INIT) != 0)
    {
       png_app_error(png_ptr,
-            "info change after png_start_read_image or png_read_update_info");
+          "info change after png_start_read_image or png_read_update_info");
       return;
    }
 #endif
diff --git a/pngwio.c b/pngwio.c
index 586c03b..37c7c3a 100644
--- a/pngwio.c
+++ b/pngwio.c
@@ -1,8 +1,8 @@
 
 /* pngwio.c - functions for data output
  *
- * Last changed in libpng 1.6.15 [November 20, 2014]
- * Copyright (c) 1998-2002,2004,2006-2014 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2014,2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -35,7 +35,7 @@
    /* NOTE: write_data_fn must not change the buffer! */
    if (png_ptr->write_data_fn != NULL )
       (*(png_ptr->write_data_fn))(png_ptr, png_constcast(png_bytep,data),
-         length);
+          length);
 
    else
       png_error(png_ptr, "Call to NULL write function");
diff --git a/pngwrite.c b/pngwrite.c
index 181a899..aaa2b01 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,8 +1,8 @@
 
 /* pngwrite.c - general routines to write a PNG file
  *
- * Last changed in libpng 1.6.19 [November 12, 2015]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -22,7 +22,7 @@
 /* Write out all the unknown chunks for the current given location */
 static void
 write_unknown_chunks(png_structrp png_ptr, png_const_inforp info_ptr,
-   unsigned int where)
+    unsigned int where)
 {
    if (info_ptr->unknown_chunks_num != 0)
    {
@@ -148,11 +148,11 @@
 #    ifdef PNG_WRITE_sRGB_SUPPORTED
                if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
                   png_app_warning(png_ptr,
-                     "profile matches sRGB but writing iCCP instead");
+                      "profile matches sRGB but writing iCCP instead");
 #     endif
 
             png_write_iCCP(png_ptr, info_ptr->iccp_name,
-               info_ptr->iccp_profile);
+                info_ptr->iccp_profile);
          }
 #     ifdef PNG_WRITE_sRGB_SUPPORTED
          else
@@ -383,7 +383,7 @@
       for (i = 0; i < info_ptr->num_text; i++)
       {
          png_debug2(2, "Writing trailer text chunk %d, type %d", i,
-            info_ptr->text[i].compression);
+             info_ptr->text[i].compression);
          /* An internationalized chunk? */
          if (info_ptr->text[i].compression > 0)
          {
@@ -693,7 +693,7 @@
       return;
 
    png_debug2(1, "in png_write_row (row %u, pass %d)",
-      png_ptr->row_number, png_ptr->pass);
+       png_ptr->row_number, png_ptr->pass);
 
    /* Initialize transformations and other stuff if first time */
    if (png_ptr->row_number == 0 && png_ptr->pass == 0)
@@ -1069,7 +1069,7 @@
              * is not available so the filter can't be used.  Just warn here.
              */
             png_app_warning(png_ptr,
-               "png_set_filter: UP/AVG/PAETH cannot be added after start");
+                "png_set_filter: UP/AVG/PAETH cannot be added after start");
             filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
          }
 
@@ -1095,13 +1095,13 @@
 
          if (png_ptr->try_row == NULL)
             png_ptr->try_row = png_voidcast(png_bytep,
-               png_malloc(png_ptr, buf_size));
+                png_malloc(png_ptr, buf_size));
 
          if (num_filters > 1)
          {
             if (png_ptr->tst_row == NULL)
                png_ptr->tst_row = png_voidcast(png_bytep,
-                  png_malloc(png_ptr, buf_size));
+                   png_malloc(png_ptr, buf_size));
          }
       }
       png_ptr->do_filter = (png_byte)filters;
@@ -1628,7 +1628,7 @@
 
 static png_byte
 png_unpremultiply(png_uint_32 component, png_uint_32 alpha,
-   png_uint_32 reciprocal/*from the above macro*/)
+    png_uint_32 reciprocal/*from the above macro*/)
 {
    /* The following gives 1.0 for an alpha of 0, which is fine, otherwise if 0/0
     * is represented as some other value there is more likely to be a
@@ -1848,16 +1848,16 @@
             if (channels >= 3) /* RGB */
             {
                palette[i].blue = png_unpremultiply(entry[afirst + (2 ^ bgr)],
-                  alpha, reciprocal);
+                   alpha, reciprocal);
                palette[i].green = png_unpremultiply(entry[afirst + 1], alpha,
-                  reciprocal);
+                   reciprocal);
                palette[i].red = png_unpremultiply(entry[afirst + bgr], alpha,
-                  reciprocal);
+                   reciprocal);
             }
 
             else /* gray */
                palette[i].blue = palette[i].red = palette[i].green =
-                  png_unpremultiply(entry[afirst], alpha, reciprocal);
+                   png_unpremultiply(entry[afirst], alpha, reciprocal);
          }
       }
 
@@ -1904,11 +1904,11 @@
 #   endif
 
    png_set_PLTE(image->opaque->png_ptr, image->opaque->info_ptr, palette,
-      entries);
+       entries);
 
    if (num_trans > 0)
       png_set_tRNS(image->opaque->png_ptr, image->opaque->info_ptr, tRNS,
-         num_trans, NULL);
+          num_trans, NULL);
 
    image->colormap_entries = entries;
 }
@@ -1917,7 +1917,7 @@
 png_image_write_main(png_voidp argument)
 {
    png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
+       argument);
    png_imagep image = display->image;
    png_structrp png_ptr = image->opaque->png_ptr;
    png_inforp info_ptr = image->opaque->info_ptr;
@@ -1980,24 +1980,24 @@
          png_uint_32 entries = image->colormap_entries;
 
          png_set_IHDR(png_ptr, info_ptr, image->width, image->height,
-            entries > 16 ? 8 : (entries > 4 ? 4 : (entries > 2 ? 2 : 1)),
-            PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
-            PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+             entries > 16 ? 8 : (entries > 4 ? 4 : (entries > 2 ? 2 : 1)),
+             PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
+             PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 
          png_image_set_PLTE(display);
       }
 
       else
          png_error(image->opaque->png_ptr,
-            "no color-map for color-mapped image");
+             "no color-map for color-mapped image");
    }
 
    else
       png_set_IHDR(png_ptr, info_ptr, image->width, image->height,
-         write_16bit ? 16 : 8,
-         ((format & PNG_FORMAT_FLAG_COLOR) ? PNG_COLOR_MASK_COLOR : 0) +
-         ((format & PNG_FORMAT_FLAG_ALPHA) ? PNG_COLOR_MASK_ALPHA : 0),
-         PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+          write_16bit ? 16 : 8,
+          ((format & PNG_FORMAT_FLAG_COLOR) ? PNG_COLOR_MASK_COLOR : 0) +
+          ((format & PNG_FORMAT_FLAG_ALPHA) ? PNG_COLOR_MASK_ALPHA : 0),
+          PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 
    /* Counter-intuitively the data transformations must be called *after*
     * png_write_info, not before as in the read code, but the 'set' functions
@@ -2012,11 +2012,11 @@
 
       if ((image->flags & PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB) == 0)
          png_set_cHRM_fixed(png_ptr, info_ptr,
-            /* color      x       y */
-            /* white */ 31270, 32900,
-            /* red   */ 64000, 33000,
-            /* green */ 30000, 60000,
-            /* blue  */ 15000,  6000
+             /* color      x       y */
+             /* white */ 31270, 32900,
+             /* red   */ 64000, 33000,
+             /* green */ 30000, 60000,
+             /* blue  */ 15000,  6000
          );
    }
 
@@ -2110,7 +2110,7 @@
        (colormap == 0 && display->convert_to_8bit != 0))
    {
       png_bytep row = png_voidcast(png_bytep, png_malloc(png_ptr,
-         png_get_rowbytes(png_ptr, info_ptr)));
+          png_get_rowbytes(png_ptr, info_ptr)));
       int result;
 
       display->local_row = row;
@@ -2150,10 +2150,10 @@
 
 static void (PNGCBAPI
 image_memory_write)(png_structp png_ptr, png_bytep/*const*/ data,
-   png_size_t size)
+    png_size_t size)
 {
    png_image_write_control *display = png_voidcast(png_image_write_control*,
-      png_ptr->io_ptr/*backdoor: png_get_io_ptr(png_ptr)*/);
+       png_ptr->io_ptr/*backdoor: png_get_io_ptr(png_ptr)*/);
    const png_alloc_size_t ob = display->output_bytes;
 
    /* Check for overflow; this should never happen: */
@@ -2184,22 +2184,22 @@
 png_image_write_memory(png_voidp argument)
 {
    png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
+       argument);
 
    /* The rest of the memory-specific init and write_main in an error protected
     * environment.  This case needs to use callbacks for the write operations
     * since libpng has no built in support for writing to memory.
     */
    png_set_write_fn(display->image->opaque->png_ptr, display/*io_ptr*/,
-         image_memory_write, image_memory_flush);
+       image_memory_write, image_memory_flush);
 
    return png_image_write_main(display);
 }
 
 int PNGAPI
 png_image_write_to_memory(png_imagep image, void *memory,
-   png_alloc_size_t * PNG_RESTRICT memory_bytes, int convert_to_8bit,
-   const void *buffer, png_int_32 row_stride, const void *colormap)
+    png_alloc_size_t * PNG_RESTRICT memory_bytes, int convert_to_8bit,
+    const void *buffer, png_int_32 row_stride, const void *colormap)
 {
    /* Write the image to the given buffer, or count the bytes if it is NULL */
    if (image != NULL && image->version == PNG_IMAGE_VERSION)
@@ -2251,12 +2251,12 @@
 
       else
          return png_image_error(image,
-            "png_image_write_to_memory: invalid argument");
+             "png_image_write_to_memory: invalid argument");
    }
 
    else if (image != NULL)
       return png_image_error(image,
-         "png_image_write_to_memory: incorrect PNG_IMAGE_VERSION");
+          "png_image_write_to_memory: incorrect PNG_IMAGE_VERSION");
 
    else
       return 0;
@@ -2265,7 +2265,7 @@
 #ifdef PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED
 int PNGAPI
 png_image_write_to_stdio(png_imagep image, FILE *file, int convert_to_8bit,
-   const void *buffer, png_int_32 row_stride, const void *colormap)
+    const void *buffer, png_int_32 row_stride, const void *colormap)
 {
    /* Write the image to the given (FILE*). */
    if (image != NULL && image->version == PNG_IMAGE_VERSION)
@@ -2301,12 +2301,12 @@
 
       else
          return png_image_error(image,
-            "png_image_write_to_stdio: invalid argument");
+             "png_image_write_to_stdio: invalid argument");
    }
 
    else if (image != NULL)
       return png_image_error(image,
-         "png_image_write_to_stdio: incorrect PNG_IMAGE_VERSION");
+          "png_image_write_to_stdio: incorrect PNG_IMAGE_VERSION");
 
    else
       return 0;
@@ -2314,8 +2314,8 @@
 
 int PNGAPI
 png_image_write_to_file(png_imagep image, const char *file_name,
-   int convert_to_8bit, const void *buffer, png_int_32 row_stride,
-   const void *colormap)
+    int convert_to_8bit, const void *buffer, png_int_32 row_stride,
+    const void *colormap)
 {
    /* Write the image to the named file. */
    if (image != NULL && image->version == PNG_IMAGE_VERSION)
@@ -2327,7 +2327,7 @@
          if (fp != NULL)
          {
             if (png_image_write_to_stdio(image, fp, convert_to_8bit, buffer,
-               row_stride, colormap) != 0)
+                row_stride, colormap) != 0)
             {
                int error; /* from fflush/fclose */
 
@@ -2368,12 +2368,12 @@
 
       else
          return png_image_error(image,
-            "png_image_write_to_file: invalid argument");
+             "png_image_write_to_file: invalid argument");
    }
 
    else if (image != NULL)
       return png_image_error(image,
-         "png_image_write_to_file: incorrect PNG_IMAGE_VERSION");
+          "png_image_write_to_file: incorrect PNG_IMAGE_VERSION");
 
    else
       return 0;
diff --git a/pngwtran.c b/pngwtran.c
index 038a2ef..423fb2d 100644
--- a/pngwtran.c
+++ b/pngwtran.c
@@ -1,8 +1,8 @@
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
- * Last changed in libpng 1.6.18 [July 23, 2015]
- * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.24 [August 4, 2016]
+ * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
@@ -525,7 +525,7 @@
 #ifdef PNG_WRITE_FILLER_SUPPORTED
    if ((png_ptr->transformations & PNG_FILLER) != 0)
       png_do_strip_channel(row_info, png_ptr->row_buf + 1,
-         !(png_ptr->flags & PNG_FLAG_FILLER_AFTER));
+          !(png_ptr->flags & PNG_FLAG_FILLER_AFTER));
 #endif
 
 #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
@@ -549,7 +549,7 @@
 #ifdef PNG_WRITE_SHIFT_SUPPORTED
    if ((png_ptr->transformations & PNG_SHIFT) != 0)
       png_do_shift(row_info, png_ptr->row_buf + 1,
-          &(png_ptr->shift));
+           &(png_ptr->shift));
 #endif
 
 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
diff --git a/pngwutil.c b/pngwutil.c
index b47f119..3f1ed0c 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,7 +1,7 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * Last changed in libpng 1.6.22 [May 26, 2016]
+ * Last changed in libpng 1.6.24 [August 4, 2016]
  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -59,7 +59,7 @@
 
    /* Write the rest of the 8 byte signature */
    png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
-      (png_size_t)(8 - png_ptr->sig_bytes));
+       (png_size_t)(8 - png_ptr->sig_bytes));
 
    if (png_ptr->sig_bytes < 3)
       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
@@ -174,7 +174,7 @@
  */
 static void
 png_write_complete_chunk(png_structrp png_ptr, png_uint_32 chunk_name,
-   png_const_bytep data, png_size_t length)
+    png_const_bytep data, png_size_t length)
 {
    if (png_ptr == NULL)
       return;
@@ -191,10 +191,10 @@
 /* This is the API that calls the internal function above. */
 void PNGAPI
 png_write_chunk(png_structrp png_ptr, png_const_bytep chunk_string,
-   png_const_bytep data, png_size_t length)
+    png_const_bytep data, png_size_t length)
 {
    png_write_complete_chunk(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), data,
-      length);
+       length);
 }
 
 /* This is used below to find the size of an image to pass to png_deflate_claim,
@@ -291,7 +291,7 @@
 /* Initialize the compressor for the appropriate type of compression. */
 static int
 png_deflate_claim(png_structrp png_ptr, png_uint_32 owner,
-   png_alloc_size_t data_size)
+    png_alloc_size_t data_size)
 {
    if (png_ptr->zowner != 0)
    {
@@ -416,7 +416,7 @@
       else
       {
          ret = deflateInit2(&png_ptr->zstream, level, method, windowBits,
-            memLevel, strategy);
+             memLevel, strategy);
 
          if (ret == Z_OK)
             png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
@@ -477,7 +477,7 @@
 
 static void
 png_text_compress_init(compression_state *comp, png_const_bytep input,
-   png_alloc_size_t input_len)
+    png_alloc_size_t input_len)
 {
    comp->input = input;
    comp->input_len = input_len;
@@ -487,7 +487,7 @@
 /* Compress the data in the compression state input */
 static int
 png_text_compress(png_structrp png_ptr, png_uint_32 chunk_name,
-   compression_state *comp, png_uint_32 prefix_len)
+    compression_state *comp, png_uint_32 prefix_len)
 {
    int ret;
 
@@ -579,7 +579,7 @@
 
          /* Compress the data */
          ret = deflate(&png_ptr->zstream,
-            input_len > 0 ? Z_NO_FLUSH : Z_FINISH);
+             input_len > 0 ? Z_NO_FLUSH : Z_FINISH);
 
          /* Claw back input data that was not consumed (because avail_in is
           * reset above every time round the loop).
@@ -925,7 +925,7 @@
  */
 void /* PRIVATE */
 png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
-   png_alloc_size_t input_len, int flush)
+    png_alloc_size_t input_len, int flush)
 {
    if (png_ptr->zowner != png_IDAT)
    {
@@ -937,7 +937,7 @@
       if (png_ptr->zbuffer_list == NULL)
       {
          png_ptr->zbuffer_list = png_voidcast(png_compression_bufferp,
-            png_malloc(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
+             png_malloc(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
          png_ptr->zbuffer_list->next = NULL;
       }
 
@@ -1358,7 +1358,7 @@
 
       /* Write the chunk out as it is */
       png_write_complete_chunk(png_ptr, png_tRNS, trans_alpha,
-         (png_size_t)num_trans);
+          (png_size_t)num_trans);
    }
 
    else if (color_type == PNG_COLOR_TYPE_GRAY)
@@ -1389,7 +1389,7 @@
 #endif
       {
          png_app_warning(png_ptr,
-           "Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
+             "Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
          return;
       }
 
@@ -1441,7 +1441,8 @@
 #endif
       {
          png_warning(png_ptr,
-             "Ignoring attempt to write 16-bit bKGD chunk when bit_depth is 8");
+             "Ignoring attempt to write 16-bit bKGD chunk "
+             "when bit_depth is 8");
 
          return;
       }
@@ -1571,7 +1572,7 @@
 
    /* Compute the compressed data; do it now for the length */
    png_text_compress_init(&comp, (png_const_bytep)text,
-      text == NULL ? 0 : strlen(text));
+       text == NULL ? 0 : strlen(text));
 
    if (png_text_compress(png_ptr, png_zTXt, &comp, key_len) != Z_OK)
       png_error(png_ptr, png_ptr->zstream.msg);
@@ -1941,7 +1942,7 @@
     */
    if ((filters & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH)) != 0)
       png_ptr->prev_row = png_voidcast(png_bytep,
-         png_calloc(png_ptr, buf_size));
+          png_calloc(png_ptr, buf_size));
 #endif /* WRITE_FILTER */
 
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
@@ -2244,7 +2245,7 @@
  */
 static void /* PRIVATE */
 png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
-   png_size_t row_bytes);
+    png_size_t row_bytes);
 
 #ifdef PNG_WRITE_FILTER_SUPPORTED
 static png_size_t /* PRIVATE */
@@ -2262,14 +2263,22 @@
         i++, rp++, dp++)
    {
       v = *dp = *rp;
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
    }
 
    for (lp = png_ptr->row_buf + 1; i < row_bytes;
       i++, rp++, lp++, dp++)
    {
       v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2278,6 +2287,28 @@
    return (sum);
 }
 
+static void /* PRIVATE */
+png_setup_sub_row_only(png_structrp png_ptr, const png_uint_32 bpp,
+    const png_size_t row_bytes)
+{
+   png_bytep rp, dp, lp;
+   png_size_t i;
+
+   png_ptr->try_row[0] = PNG_FILTER_VALUE_SUB;
+
+   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1; i < bpp;
+        i++, rp++, dp++)
+   {
+      *dp = *rp;
+   }
+
+   for (lp = png_ptr->row_buf + 1; i < row_bytes;
+      i++, rp++, lp++, dp++)
+   {
+      *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
+   }
+}
+
 static png_size_t /* PRIVATE */
 png_setup_up_row(png_structrp png_ptr, const png_size_t row_bytes,
     const png_size_t lmins)
@@ -2294,7 +2325,11 @@
        i++, rp++, pp++, dp++)
    {
       v = *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2302,10 +2337,25 @@
 
    return (sum);
 }
+static void /* PRIVATE */
+png_setup_up_row_only(png_structrp png_ptr, const png_size_t row_bytes)
+{
+   png_bytep rp, dp, pp;
+   png_size_t i;
+
+   png_ptr->try_row[0] = PNG_FILTER_VALUE_UP;
+
+   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
+       pp = png_ptr->prev_row + 1; i < row_bytes;
+       i++, rp++, pp++, dp++)
+   {
+      *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
+   }
+}
 
 static png_size_t /* PRIVATE */
 png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
-      const png_size_t row_bytes, const png_size_t lmins)
+    const png_size_t row_bytes, const png_size_t lmins)
 {
    png_bytep rp, dp, pp, lp;
    png_uint_32 i;
@@ -2315,11 +2365,15 @@
    png_ptr->try_row[0] = PNG_FILTER_VALUE_AVG;
 
    for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
-        pp = png_ptr->prev_row + 1; i < bpp; i++)
+       pp = png_ptr->prev_row + 1; i < bpp; i++)
    {
       v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
    }
 
    for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
@@ -2327,7 +2381,11 @@
       v = *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
           & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2335,6 +2393,27 @@
 
    return (sum);
 }
+static void /* PRIVATE */
+png_setup_avg_row_only(png_structrp png_ptr, const png_uint_32 bpp,
+    const png_size_t row_bytes)
+{
+   png_bytep rp, dp, pp, lp;
+   png_uint_32 i;
+
+   png_ptr->try_row[0] = PNG_FILTER_VALUE_AVG;
+
+   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
+       pp = png_ptr->prev_row + 1; i < bpp; i++)
+   {
+      *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
+   }
+
+   for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
+   {
+      *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
+          & 0xff);
+   }
+}
 
 static png_size_t /* PRIVATE */
 png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
@@ -2352,7 +2431,11 @@
    {
       v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
    }
 
    for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
@@ -2381,7 +2464,11 @@
 
       v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2389,6 +2476,48 @@
 
    return (sum);
 }
+static void /* PRIVATE */
+png_setup_paeth_row_only(png_structrp png_ptr, const png_uint_32 bpp,
+    const png_size_t row_bytes)
+{
+   png_bytep rp, dp, pp, cp, lp;
+   png_size_t i;
+
+   png_ptr->try_row[0] = PNG_FILTER_VALUE_PAETH;
+
+   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
+       pp = png_ptr->prev_row + 1; i < bpp; i++)
+   {
+      *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
+   }
+
+   for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
+        i++)
+   {
+      int a, b, c, pa, pb, pc, p;
+
+      b = *pp++;
+      c = *cp++;
+      a = *lp++;
+
+      p = b - c;
+      pc = a - c;
+
+#ifdef PNG_USE_ABS
+      pa = abs(p);
+      pb = abs(pc);
+      pc = abs(p + pc);
+#else
+      pa = p < 0 ? -p : p;
+      pb = pc < 0 ? -pc : pc;
+      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#endif
+
+      p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
+
+      *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
+   }
+}
 #endif /* WRITE_FILTER */
 
 void /* PRIVATE */
@@ -2397,7 +2526,7 @@
 #ifndef PNG_WRITE_FILTER_SUPPORTED
    png_write_filtered_row(png_ptr, png_ptr->row_buf, row_info->rowbytes+1);
 #else
-   png_byte filter_to_do = png_ptr->do_filter;
+   unsigned int filter_to_do = png_ptr->do_filter;
    png_bytep row_buf;
    png_bytep best_row;
    png_uint_32 bpp;
@@ -2443,32 +2572,33 @@
     */
    best_row = png_ptr->row_buf;
 
-
-   if ((filter_to_do & PNG_FILTER_NONE) != 0 && filter_to_do != PNG_FILTER_NONE)
+   if (PNG_SIZE_MAX/128 <= row_bytes)
    {
+      /* Overflow can occur in the calculation, just select the lowest set
+       * filter.
+       */
+      filter_to_do &= 0U-filter_to_do;
+   }
+   else if ((filter_to_do & PNG_FILTER_NONE) != 0 &&
+         filter_to_do != PNG_FILTER_NONE)
+   {
+      /* Overflow not possible and multiple filters in the list, including the
+       * 'none' filter.
+       */
       png_bytep rp;
       png_size_t sum = 0;
       png_size_t i;
       int v;
 
-      if (PNG_SIZE_MAX/128 <= row_bytes)
-      {
-         for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
-         {
-            /* Check for overflow */
-            if (sum > PNG_SIZE_MAX/128 - 256)
-               break;
-
-            v = *rp;
-            sum += (v < 128) ? v : 256 - v;
-         }
-      }
-      else /* Overflow is not possible */
       {
          for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
          {
             v = *rp;
+#ifdef PNG_USE_ABS
+            sum += 128 - abs(v - 128);
+#else
             sum += (v < 128) ? v : 256 - v;
+#endif
          }
       }
 
@@ -2479,7 +2609,7 @@
    if (filter_to_do == PNG_FILTER_SUB)
    /* It's the only filter so no testing is needed */
    {
-      (void) png_setup_sub_row(png_ptr, bpp, row_bytes, mins);
+      png_setup_sub_row_only(png_ptr, bpp, row_bytes);
       best_row = png_ptr->try_row;
    }
 
@@ -2505,7 +2635,7 @@
    /* Up filter */
    if (filter_to_do == PNG_FILTER_UP)
    {
-      (void) png_setup_up_row(png_ptr, row_bytes, mins);
+      png_setup_up_row_only(png_ptr, row_bytes);
       best_row = png_ptr->try_row;
    }
 
@@ -2531,7 +2661,7 @@
    /* Avg filter */
    if (filter_to_do == PNG_FILTER_AVG)
    {
-      (void) png_setup_avg_row(png_ptr, bpp, row_bytes, mins);
+      png_setup_avg_row_only(png_ptr, bpp, row_bytes);
       best_row = png_ptr->try_row;
    }
 
@@ -2555,9 +2685,9 @@
    }
 
    /* Paeth filter */
-   if ((filter_to_do == PNG_FILTER_PAETH) != 0)
+   if (filter_to_do == PNG_FILTER_PAETH)
    {
-      (void) png_setup_paeth_row(png_ptr, bpp, row_bytes, mins);
+      png_setup_paeth_row_only(png_ptr, bpp, row_bytes);
       best_row = png_ptr->try_row;
    }
 
@@ -2589,7 +2719,7 @@
 /* Do the actual writing of a previously filtered row. */
 static void
 png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
-   png_size_t full_row_length/*includes filter byte*/)
+    png_size_t full_row_length/*includes filter byte*/)
 {
    png_debug(1, "in png_write_filtered_row");
 
diff --git a/projects/vstudio/README.txt b/projects/vstudio/README.txt
index e275173..0aabdb7 100644
--- a/projects/vstudio/README.txt
+++ b/projects/vstudio/README.txt
@@ -1,7 +1,7 @@
 
 VisualStudio instructions
 
-libpng version 1.6.23 - June 9, 2016
+libpng version 1.6.24 - August 4, 2016
 
 Copyright (c) 2010,2013,2015 Glenn Randers-Pehrson
 
@@ -93,3 +93,5 @@
     DLL               /MD         /MDd
     Static Library    /MD         /MDd
 
+Also, be sure to build libpng, zlib, and your project all for the same
+platform (e.g., 32-bit or 64-bit).
diff --git a/projects/vstudio/libpng/libpng.vcxproj b/projects/vstudio/libpng/libpng.vcxproj
index de7fc3c..9bfb718 100644
--- a/projects/vstudio/libpng/libpng.vcxproj
+++ b/projects/vstudio/libpng/libpng.vcxproj
@@ -84,7 +84,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <PrecompiledHeader>Use</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
@@ -97,9 +97,9 @@
       <BrowseInformation>true</BrowseInformation>
       <CompileAs>CompileAsC</CompileAs>
       <StringPooling>true</StringPooling>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <Optimization>Disabled</Optimization>
       <RuntimeLibrary>MultiThreadedDebugDLL</RuntimeLibrary>
     </ClCompile>
@@ -114,7 +114,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug Library|Win32'">
     <ClCompile>
       <PrecompiledHeader>Use</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
@@ -128,9 +128,9 @@
       <BrowseInformation>true</BrowseInformation>
       <CompileAs>CompileAsC</CompileAs>
       <StringPooling>true</StringPooling>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
     </ClCompile>
     <Link>
@@ -140,7 +140,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>Use</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <FunctionLevelLinking>true</FunctionLevelLinking>
@@ -153,9 +153,9 @@
       <CompileAs>CompileAsC</CompileAs>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <Optimization>Full</Optimization>
     </ClCompile>
     <Link>
@@ -170,7 +170,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release Library|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>Use</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
@@ -184,9 +184,9 @@
       <CompileAs>CompileAsC</CompileAs>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <Optimization>Full</Optimization>
       <WholeProgramOptimization>true</WholeProgramOptimization>
     </ClCompile>
diff --git a/projects/vstudio/pnglibconf/pnglibconf.vcxproj b/projects/vstudio/pnglibconf/pnglibconf.vcxproj
index e2a232c..efcc440 100644
--- a/projects/vstudio/pnglibconf/pnglibconf.vcxproj
+++ b/projects/vstudio/pnglibconf/pnglibconf.vcxproj
@@ -30,7 +30,7 @@
   </PropertyGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <WarningLevel>Level3</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
diff --git a/projects/vstudio/pngstest/pngstest.vcxproj b/projects/vstudio/pngstest/pngstest.vcxproj
index 0d2980d..21810e3 100644
--- a/projects/vstudio/pngstest/pngstest.vcxproj
+++ b/projects/vstudio/pngstest/pngstest.vcxproj
@@ -76,16 +76,16 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -109,7 +109,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug Library|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
@@ -117,9 +117,9 @@
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -141,7 +141,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -149,9 +149,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
@@ -176,7 +176,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release Library|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -185,9 +185,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
diff --git a/projects/vstudio/pngtest/pngtest.vcxproj b/projects/vstudio/pngtest/pngtest.vcxproj
index bf9266f..f1df07d 100644
--- a/projects/vstudio/pngtest/pngtest.vcxproj
+++ b/projects/vstudio/pngtest/pngtest.vcxproj
@@ -76,16 +76,16 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -109,7 +109,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug Library|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
@@ -117,9 +117,9 @@
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -141,7 +141,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -149,9 +149,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
@@ -176,7 +176,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release Library|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -185,9 +185,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
diff --git a/projects/vstudio/pngunknown/pngunknown.vcxproj b/projects/vstudio/pngunknown/pngunknown.vcxproj
index a30cc7a..409d662 100644
--- a/projects/vstudio/pngunknown/pngunknown.vcxproj
+++ b/projects/vstudio/pngunknown/pngunknown.vcxproj
@@ -76,16 +76,16 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -109,7 +109,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug Library|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
@@ -117,9 +117,9 @@
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -141,7 +141,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -149,9 +149,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
@@ -176,7 +176,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release Library|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -185,9 +185,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
diff --git a/projects/vstudio/pngvalid/pngvalid.vcxproj b/projects/vstudio/pngvalid/pngvalid.vcxproj
index 07cf241..c117d29 100644
--- a/projects/vstudio/pngvalid/pngvalid.vcxproj
+++ b/projects/vstudio/pngvalid/pngvalid.vcxproj
@@ -76,16 +76,16 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -109,7 +109,7 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug Library|Win32'">
     <ClCompile>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <MinimalRebuild>false</MinimalRebuild>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
@@ -117,9 +117,9 @@
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
       <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <StringPooling>true</StringPooling>
       <FunctionLevelLinking>false</FunctionLevelLinking>
@@ -141,7 +141,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -149,9 +149,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
@@ -176,7 +176,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release Library|Win32'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <PrecompiledHeader>NotUsing</PrecompiledHeader>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
@@ -185,9 +185,9 @@
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <StringPooling>true</StringPooling>
       <MinimalRebuild>false</MinimalRebuild>
       <BrowseInformation>true</BrowseInformation>
diff --git a/projects/vstudio/zlib.props b/projects/vstudio/zlib.props
index f64a227..8d370b2 100644
--- a/projects/vstudio/zlib.props
+++ b/projects/vstudio/zlib.props
@@ -2,7 +2,7 @@
 <!--
  * zlib.props - location of zlib source
  *
- * libpng version 1.6.23 - June 9, 2016
+ * libpng version 1.6.24 - August 4, 2016
  *
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  *
@@ -41,5 +41,18 @@
          test it:
      -->
     <WindowsSDKDesktopARMSupport>true</WindowsSDKDesktopARMSupport>
+
+    <!-- The following lines provide a global (solution level) control of the
+         warnings issued by the compiler, these are used in the individual
+         project files (*/*.vcxproj) with, for zlib, some extra disables.
+
+         Different versions of Visual Studio may require different settings,
+         these settings work with Visual Studio 2013.  Just set
+         TreatWarningAsError to false to check the build without failing on
+         errors.
+     -->
+   <WarningLevel>EnableAllWarnings</WarningLevel>
+   <TreatWarningAsError>true</TreatWarningAsError>
+   <DisableSpecificWarnings>4255;4668;4710;4711;4746;4820;4996</DisableSpecificWarnings>
   </PropertyGroup>
 </Project>
diff --git a/projects/vstudio/zlib/zlib.vcxproj b/projects/vstudio/zlib/zlib.vcxproj
index 6e5b94a..0df16db 100644
--- a/projects/vstudio/zlib/zlib.vcxproj
+++ b/projects/vstudio/zlib/zlib.vcxproj
@@ -88,11 +88,13 @@
     <ClCompile>
       <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;Z_SOLO;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
-      <WarningLevel>TurnOffAllWarnings</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BrowseInformation>true</BrowseInformation>
       <FunctionLevelLinking>true</FunctionLevelLinking>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings);4127;4131;4242;4244</DisableSpecificWarnings>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
     </ClCompile>
     <Link>
       <TargetMachine>MachineX86</TargetMachine>
@@ -103,11 +105,13 @@
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
       <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;Z_SOLO;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-      <WarningLevel>TurnOffAllWarnings</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BrowseInformation>true</BrowseInformation>
       <FunctionLevelLinking>true</FunctionLevelLinking>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings);4127;4131;4242;4244</DisableSpecificWarnings>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <RuntimeLibrary>MultiThreadedDebugDLL</RuntimeLibrary>
     </ClCompile>
     <Link>
@@ -118,7 +122,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release Library|Win32'">
     <ClCompile>
-      <WarningLevel>Level3</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
       <IntrinsicFunctions>true</IntrinsicFunctions>
@@ -126,7 +130,8 @@
       <BufferSecurityCheck>false</BufferSecurityCheck>
       <BrowseInformation>true</BrowseInformation>
       <FunctionLevelLinking>true</FunctionLevelLinking>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings);4127;4131;4242;4244</DisableSpecificWarnings>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
       <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;Z_SOLO;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
@@ -141,7 +146,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <WarningLevel>Level3</WarningLevel>
+      <WarningLevel>$(WarningLevel)</WarningLevel>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Full</Optimization>
       <IntrinsicFunctions>true</IntrinsicFunctions>
@@ -149,7 +154,8 @@
       <BufferSecurityCheck>false</BufferSecurityCheck>
       <BrowseInformation>true</BrowseInformation>
       <FunctionLevelLinking>true</FunctionLevelLinking>
-      <TreatWarningAsError>true</TreatWarningAsError>
+      <DisableSpecificWarnings>$(DisableSpecificWarnings);4127;4131;4242;4244</DisableSpecificWarnings>
+      <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
       <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;Z_SOLO;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
     <Link>
diff --git a/scripts/README.txt b/scripts/README.txt
index 7f83431..56933f2 100644
--- a/scripts/README.txt
+++ b/scripts/README.txt
@@ -1,9 +1,9 @@
 
-Makefiles for  libpng version 1.6.23 - June 9, 2016
+Makefiles for  libpng version 1.6.24 - August 4, 2016
 
 pnglibconf.h.prebuilt       =>  Stores configuration settings
  makefile.linux    =>  Linux/ELF makefile
-                       (gcc, creates libpng16.so.16.1.6.23)
+                       (gcc, creates libpng16.so.16.1.6.24)
  makefile.gcc      =>  Generic makefile (gcc, creates static libpng.a)
  makefile.knr      =>  Archaic UNIX Makefile that converts files with
                        ansi2knr (Requires ansi2knr.c from
@@ -33,12 +33,12 @@
  makefile.os2      =>  OS/2 Makefile (gcc and emx, requires libpng.def)
  makefile.sco      =>  For SCO OSr5  ELF and Unixware 7 with Native cc
  makefile.sggcc    =>  Silicon Graphics (gcc,
-                       creates libpng16.so.16.1.6.23)
+                       creates libpng16.so.16.1.6.24)
  makefile.sgi      =>  Silicon Graphics IRIX makefile (cc, creates static lib)
  makefile.solaris  =>  Solaris 2.X makefile (gcc,
-                       creates libpng16.so.16.1.6.23)
+                       creates libpng16.so.16.1.6.24)
  makefile.so9      =>  Solaris 9 makefile (gcc,
-                       creates libpng16.so.16.1.6.23)
+                       creates libpng16.so.16.1.6.24)
  makefile.std      =>  Generic UNIX makefile (cc, creates static libpng.a)
  makefile.sunos    =>  Sun makefile
  makefile.32sunu   =>  Sun Ultra 32-bit makefile
diff --git a/scripts/def.c b/scripts/def.c
index caf174d..7c04875 100644
--- a/scripts/def.c
+++ b/scripts/def.c
@@ -21,7 +21,7 @@
 PNG_DFN "OS2 CODE PRELOAD MOVEABLE DISCARDABLE"
 PNG_DFN ""
 PNG_DFN "EXPORTS"
-PNG_DFN ";Version 1.6.23"
+PNG_DFN ";Version 1.6.24"
 
 #define PNG_EXPORTA(ordinal, type, name, args, attributes)\
         PNG_DFN "@" SYMBOL_PREFIX "@@" name "@"
diff --git a/scripts/libpng-config-head.in b/scripts/libpng-config-head.in
index df11744..b0c6e38 100644
--- a/scripts/libpng-config-head.in
+++ b/scripts/libpng-config-head.in
@@ -11,7 +11,7 @@
 
 # Modeled after libxml-config.
 
-version=1.6.23
+version=1.6.24
 prefix=""
 libdir=""
 libs=""
diff --git a/scripts/libpng.pc.in b/scripts/libpng.pc.in
index e5e0eac..bed81d3 100644
--- a/scripts/libpng.pc.in
+++ b/scripts/libpng.pc.in
@@ -5,6 +5,6 @@
 
 Name: libpng
 Description: Loads and saves PNG files
-Version: 1.6.23
+Version: 1.6.24
 Libs: -L${libdir} -lpng16
 Cflags: -I${includedir}
diff --git a/scripts/makefile.cegcc b/scripts/makefile.cegcc
index bcd661c..fb1361b 100644
--- a/scripts/makefile.cegcc
+++ b/scripts/makefile.cegcc
@@ -23,7 +23,7 @@
 
 VERMAJ = 1
 VERMIN = 6
-VERMIC = 23
+VERMIC = 24
 VER = $(VERMAJ).$(VERMIN).$(VERMIC)
 NAME = libpng
 PACKAGE = $(NAME)-$(VER)
diff --git a/scripts/makefile.linux b/scripts/makefile.linux
index cfa236b..af0d65e 100644
--- a/scripts/makefile.linux
+++ b/scripts/makefile.linux
@@ -10,7 +10,7 @@
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 23
+RELEASE = 24
 
 # Shared library names:
 LIBSO=$(LIBNAME).so
diff --git a/scripts/makefile.msys b/scripts/makefile.msys
index cf8a29d..ddbd88c 100644
--- a/scripts/makefile.msys
+++ b/scripts/makefile.msys
@@ -18,7 +18,7 @@
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 23
+RELEASE = 24
 
 # Shared library names:
 LIBSO=$(LIBNAME).dll
diff --git a/scripts/makefile.ne12bsd b/scripts/makefile.ne12bsd
index 6106021..d18bdb1 100644
--- a/scripts/makefile.ne12bsd
+++ b/scripts/makefile.ne12bsd
@@ -17,7 +17,7 @@
 
 LIB=	png16
 SHLIB_MAJOR=	0
-SHLIB_MINOR=	1.6.23
+SHLIB_MINOR=	1.6.24
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
diff --git a/scripts/makefile.netbsd b/scripts/makefile.netbsd
index a46644a..85c2ea4 100644
--- a/scripts/makefile.netbsd
+++ b/scripts/makefile.netbsd
@@ -17,7 +17,7 @@
 
 LIB=	png
 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.23
+SHLIB_MINOR=	1.6.24
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
diff --git a/scripts/makefile.openbsd b/scripts/makefile.openbsd
index 22ca136..07b8183 100644
--- a/scripts/makefile.openbsd
+++ b/scripts/makefile.openbsd
@@ -11,7 +11,7 @@
 MANDIR= ${PREFIX}/man/cat
 
 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.23
+SHLIB_MINOR=	1.6.24
 
 LIB=	png
 SRCS=	png.c pngerror.c pngget.c pngmem.c pngpread.c \
diff --git a/scripts/pnglibconf.dfa b/scripts/pnglibconf.dfa
index 2c936c2..019c06d 100644
--- a/scripts/pnglibconf.dfa
+++ b/scripts/pnglibconf.dfa
@@ -552,6 +552,7 @@
 
 # These options disable *all* the text chunks if turned off
 
+option TEXT disabled
 option READ_TEXT requires READ_ANCILLARY_CHUNKS enables TEXT
 option WRITE_TEXT requires WRITE_ANCILLARY_CHUNKS enables TEXT
 
diff --git a/scripts/pnglibconf.h.prebuilt b/scripts/pnglibconf.h.prebuilt
index 3e70aa1..d91d9f4 100644
--- a/scripts/pnglibconf.h.prebuilt
+++ b/scripts/pnglibconf.h.prebuilt
@@ -1,8 +1,8 @@
-/* libpng 1.6.23 STANDARD API DEFINITION */
+/* libpng 1.6.24 STANDARD API DEFINITION */
 
 /* pnglibconf.h - library build configuration */
 
-/* Libpng version 1.6.23 - June 9, 2016 */
+/* Libpng version 1.6.24 - August 4, 2016 */
 
 /* Copyright (c) 1998-2015 Glenn Randers-Pehrson */
 
diff --git a/scripts/symbols.def b/scripts/symbols.def
index 35fd39d..d3851f5 100644
--- a/scripts/symbols.def
+++ b/scripts/symbols.def
@@ -1,4 +1,4 @@
-;Version 1.6.23
+;Version 1.6.24
 ;--------------------------------------------------------------
 ; LIBPNG symbol list as a Win32 DEF file
 ; Contains all the symbols that can be exported from libpng