diff --git a/ANNOUNCE b/ANNOUNCE
index 4c5ce17..3621e64 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.5.0beta17 - April 1, 2010
+Libpng 1.5.0beta17 - April 17, 2010
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -142,7 +142,13 @@
   Combined multiple png_warning() calls for a single error.
   Restored the macro definition of png_check_sig().
 
-version 1.5.0beta17 [April 1, 2010]
+version 1.5.0beta17 [April 17, 2010]
+  Documented the fact that png_set_dither() was disabled since libpng-1.4.0.
+  Reenabled png_set_dither() but renamed it to png_set_quantize() to reflect
+    more accurately what it actually does.  At the same time, renamed
+    the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros to
+    PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
+  Added some "(long)" typecasts to printf calls in png_handle_cHRM().
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 56b386f..36a488e 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2054,7 +2054,7 @@
     PNG_TRANSFORM_STRIP_FILLER (Jim Barry).
 
 version 1.4.0beta47 [December 15, 2008]
-  Support for dithering was removed by default, because it has never
+  Support for dithering was disabled by default, because it has never
     been well tested and doesn't work very well.  The code has not
     been removed, however, and can be enabled by building libpng with
     PNG_READ_DITHER_SUPPORTED defined.
@@ -2611,7 +2611,7 @@
   Removed makefile.mingw.
   Eliminated PNG_NO_EXTERN and PNG_ALL_EXTERN
 
-version 1.5.0beta16 [April 14, 2010]
+version 1.5.0beta16 [April 1, 2010]
   Make png_text_struct independent of PNG_iTXt_SUPPORTED, so that
     fields are initialized in all configurations.  The READ/WRITE
     macros (PNG_(READ|WRITE)_iTXt_SUPPORTED) still function as
@@ -2622,6 +2622,15 @@
   Combined multiple png_warning() calls for a single error.
   Restored the macro definition of png_check_sig().
 
+version 1.5.0beta17 [April 17, 2010]
+  Added some "(long)" typecasts to printf calls in png_handle_cHRM().
+  Documented the fact that png_set_dither() was disabled since libpng-1.4.0.
+  Reenabled png_set_dither() but renamed it to png_set_quantize() to reflect
+    more accurately what it actually does.  At the same time, renamed
+    the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros to
+    PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
+  Added some "(long)" typecasts to printf calls in png_handle_cHRM().
+
 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/INSTALL b/INSTALL
index 53271d1..f83e5f9 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,5 +1,5 @@
 
-Installing libpng version 1.5.0beta17 - April 1, 2010
+Installing libpng version 1.5.0beta17 - April 17, 2010
 
 On Unix/Linux and similar systems, you can simply type
 
diff --git a/LICENSE b/LICENSE
index b31070f..e52470e 100644
--- a/LICENSE
+++ b/LICENSE
@@ -10,7 +10,7 @@
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.0beta17, April 1, 2010, are
+libpng versions 1.2.6, August 15, 2004, through 1.5.0beta17, April 17, 2010, are
 Copyright (c) 2004, 2006-2007 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.2.5
 with the following individual added to the list of Contributing Authors
@@ -108,4 +108,4 @@
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-April 1, 2010
+April 17, 2010
diff --git a/README b/README
index cc5cb87..fc97f13 100644
--- a/README
+++ b/README
@@ -1,4 +1,4 @@
-README for libpng version 1.5.0beta17 - April 1, 2010 (shared library 15.0)
+README for libpng version 1.5.0beta17 - April 17, 2010 (shared library 15.0)
 See the note about version numbers near the top of png.h
 
 See INSTALL for instructions on how to install libpng.
diff --git a/contrib/pngminim/decoder/pngusr.h b/contrib/pngminim/decoder/pngusr.h
index 9cbfc53..6e40d64 100644
--- a/contrib/pngminim/decoder/pngusr.h
+++ b/contrib/pngminim/decoder/pngusr.h
@@ -25,7 +25,7 @@
 
 #define PNG_NO_READ_GAMMA
 #define PNG_NO_READ_BACKGROUND
-#define PNG_NO_READ_DITHER
+#define PNG_NO_READ_QUANTIZE
 #define PNG_NO_READ_INVERT
 #define PNG_NO_READ_SHIFT
 #define PNG_NO_READ_PACK
diff --git a/contrib/pngminim/encoder/pngusr.h b/contrib/pngminim/encoder/pngusr.h
index 2feed2e..02eeaa8 100644
--- a/contrib/pngminim/encoder/pngusr.h
+++ b/contrib/pngminim/encoder/pngusr.h
@@ -23,7 +23,7 @@
 
 #define PNG_NO_WRITE_BACKGROUND
 #define PNG_NO_WRITE_GAMMA
-#define PNG_NO_WRITE_DITHER
+#define PNG_NO_WRITE_QUANTIZE
 #define PNG_NO_WRITE_INVERT
 #define PNG_NO_WRITE_SHIFT
 #define PNG_NO_WRITE_PACK
diff --git a/contrib/pngminim/preader/pngusr.h b/contrib/pngminim/preader/pngusr.h
index ca851e0..6f6d0ce 100644
--- a/contrib/pngminim/preader/pngusr.h
+++ b/contrib/pngminim/preader/pngusr.h
@@ -19,7 +19,7 @@
 #define png_error(s1,s2) png_err(s1)
 #define png_chunk_error(s1,s2) png_err(s1)
 
-#define PNG_NO_READ_DITHER
+#define PNG_NO_READ_QUANTIZE
 #define PNG_NO_READ_INVERT
 #define PNG_NO_READ_SHIFT
 #define PNG_NO_READ_PACK
diff --git a/example.c b/example.c
index 76d323f..48298d2 100644
--- a/example.c
+++ b/example.c
@@ -2,7 +2,7 @@
 #if 0 /* in case someone actually tries to compile this */
 
 /* example.c - an example of using libpng
- * Last changed in libpng 1.5.0 [April 14, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * This file has been placed in the public domain by the authors.
  * Maintained 1998-2010 Glenn Randers-Pehrson
  * Maintained 1996, 1997 Andreas Dilger)
@@ -160,7 +160,7 @@
     * If you have enough memory to read in the entire image at once,
     * and you need to specify only transforms that can be controlled
     * with one of the PNG_TRANSFORM_* bits (this presently excludes
-    * dithering, filling, setting background, and doing gamma
+    * quantizing, filling, setting background, and doing gamma
     * adjustment), then you can read the entire image (including
     * pixels) into the info structure with this call:
     */
@@ -271,8 +271,8 @@
          png_set_gamma(png_ptr, screen_gamma, 0.45455);
    }
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   /* Dither RGB files down to 8 bit palette or reduce palettes
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   /* Quantize RGB files down to 8 bit palette or reduce palettes
     * to the number of colors available on your screen.
     */
    if (color_type & PNG_COLOR_MASK_COLOR)
@@ -283,10 +283,10 @@
       /* This reduces the image to the application supplied palette */
       if (/* We have our own palette */)
       {
-         /* An array of colors to which the image should be dithered */
+         /* An array of colors to which the image should be quantized */
          png_color std_color_cube[MAX_SCREEN_COLORS];
 
-         png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
+         png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
             MAX_SCREEN_COLORS, NULL, 0);
       }
       /* This reduces the image to the palette supplied in the file */
@@ -296,11 +296,11 @@
 
          png_get_hIST(png_ptr, info_ptr, &histogram);
 
-         png_set_dither(png_ptr, palette, num_palette,
+         png_set_quantize(png_ptr, palette, num_palette,
                         max_screen_colors, histogram, 0);
       }
    }
-#endif /* PNG_READ_DITHER_SUPPORTED */
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
 
    /* Invert monochrome files to have 0 as white and 1 as black */
    png_set_invert_mono(png_ptr);
diff --git a/libpng-1.5.0beta17.txt b/libpng-1.5.0beta17.txt
index 7963d8d..07642f2 100644
--- a/libpng-1.5.0beta17.txt
+++ b/libpng-1.5.0beta17.txt
@@ -1,6 +1,6 @@
 libpng.txt - A description on how to use and modify libpng
 
- libpng version 1.5.0beta17 - April 14, 2010
+ libpng version 1.5.0beta17 - April 17, 2010
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
@@ -11,7 +11,7 @@
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.5.0beta17 - April 14, 2010
+ libpng versions 0.97, January 1998, through 1.5.0beta17 - April 17, 2010
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
 
@@ -479,7 +479,7 @@
                                 to RGB (or GA to RGBA)
 
 (This excludes setting a background color, doing gamma transformation,
-dithering, and setting filler.)  If this is the case, simply do this:
+quantizing, and setting filler.)  If this is the case, simply do this:
 
     png_read_png(png_ptr, info_ptr, png_transforms, NULL)
 
@@ -1166,6 +1166,40 @@
    else
       png_set_gamma(png_ptr, screen_gamma, 0.45455);
 
+If you need to reduce an RGB file to a paletted file, or if a paletted
+file has more entries then will fit on your screen, png_set_quantize()
+will do that.  Note that this is a simple match dither that merely
+finds the closest color available.  This should work fairly well with
+optimized palettes, and fairly badly with linear color cubes.  If you
+pass a palette that is larger then maximum_colors, the file will
+reduce the number of colors in the palette so it will fit into
+maximum_colors.  If there is a histogram, it will use it to make
+more intelligent choices when reducing the palette.  If there is no
+histogram, it may not do as good a job.
+
+   if (color_type & PNG_COLOR_MASK_COLOR)
+   {
+      if (png_get_valid(png_ptr, info_ptr,
+         PNG_INFO_PLTE))
+      {
+         png_uint_16p histogram = NULL;
+
+         png_get_hIST(png_ptr, info_ptr,
+            &histogram);
+         png_set_quantize(png_ptr, palette, num_palette,
+            max_screen_colors, histogram, 1);
+      }
+      else
+      {
+         png_color std_color_cube[MAX_SCREEN_COLORS] =
+            { ... colors ... };
+
+         png_set_quantize(png_ptr, std_color_cube,
+            MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
+            NULL,0);
+      }
+   }
+
 PNG files describe monochrome as black being zero and white being one.
 The following code will reverse this (make black be one and white be
 zero):
@@ -3118,10 +3152,14 @@
 The png_zalloc() function no longer zeroes out the memory that it
 allocates.
 
-Support for dithering was removed by default, because it has never
-been well tested and doesn't work very well.  The code has not
-been removed, however, and can be enabled by building libpng with
-PNG_READ_DITHER_SUPPORTED defined.
+Support for dithering was disabled by default in libpng-1.4.0, because
+been well tested and doesn't actually "dither".  The code was not
+removed, however, and could be enabled by building libpng with
+PNG_READ_DITHER_SUPPORTED defined.  In libpng-1.4.2, this support
+was reenabled, but the function was renamed png_set_quantize() to
+reflect more accurately what it actually does.  At the same time,
+the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
+PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
 
 We removed the trailing '.' from the warning and error messages.
 
@@ -3263,7 +3301,7 @@
 
 XIII. Y2K Compliance in libpng
 
-April 14, 2010
+April 17, 2010
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
diff --git a/libpng.3 b/libpng.3
index 36cf625..c3a5a8a 100644
--- a/libpng.3
+++ b/libpng.3
@@ -1,4 +1,4 @@
-.TH LIBPNG 3 "April 14, 2010"
+.TH LIBPNG 3 "April 17, 2010"
 .SH NAME
 libpng \- Portable Network Graphics (PNG) Reference Library 1.5.0beta17
 .SH SYNOPSIS
@@ -458,10 +458,6 @@
 
 \fI\fB
 
-\fBvoid png_set_dither (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_dither\fP\fB);\fP
-
-\fI\fB
-
 \fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP
 
 \fI\fB
@@ -586,6 +582,10 @@
 
 \fI\fB
 
+\fBvoid png_set_quantize (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_quantize\fP\fB);\fP
+
+\fI\fB
+
 \fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP
 
 \fI\fB
@@ -789,7 +789,7 @@
 .SH LIBPNG.TXT
 libpng.txt - A description on how to use and modify libpng
 
- libpng version 1.5.0beta17 - April 14, 2010
+ libpng version 1.5.0beta17 - April 17, 2010
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
@@ -800,7 +800,7 @@
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.5.0beta17 - April 14, 2010
+ libpng versions 0.97, January 1998, through 1.5.0beta17 - April 17, 2010
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
 
@@ -1268,7 +1268,7 @@
                                 to RGB (or GA to RGBA)
 
 (This excludes setting a background color, doing gamma transformation,
-dithering, and setting filler.)  If this is the case, simply do this:
+quantizing, and setting filler.)  If this is the case, simply do this:
 
     png_read_png(png_ptr, info_ptr, png_transforms, NULL)
 
@@ -1955,6 +1955,40 @@
    else
       png_set_gamma(png_ptr, screen_gamma, 0.45455);
 
+If you need to reduce an RGB file to a paletted file, or if a paletted
+file has more entries then will fit on your screen, png_set_quantize()
+will do that.  Note that this is a simple match dither that merely
+finds the closest color available.  This should work fairly well with
+optimized palettes, and fairly badly with linear color cubes.  If you
+pass a palette that is larger then maximum_colors, the file will
+reduce the number of colors in the palette so it will fit into
+maximum_colors.  If there is a histogram, it will use it to make
+more intelligent choices when reducing the palette.  If there is no
+histogram, it may not do as good a job.
+
+   if (color_type & PNG_COLOR_MASK_COLOR)
+   {
+      if (png_get_valid(png_ptr, info_ptr,
+         PNG_INFO_PLTE))
+      {
+         png_uint_16p histogram = NULL;
+
+         png_get_hIST(png_ptr, info_ptr,
+            &histogram);
+         png_set_quantize(png_ptr, palette, num_palette,
+            max_screen_colors, histogram, 1);
+      }
+      else
+      {
+         png_color std_color_cube[MAX_SCREEN_COLORS] =
+            { ... colors ... };
+
+         png_set_quantize(png_ptr, std_color_cube,
+            MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
+            NULL,0);
+      }
+   }
+
 PNG files describe monochrome as black being zero and white being one.
 The following code will reverse this (make black be one and white be
 zero):
@@ -3907,10 +3941,14 @@
 The png_zalloc() function no longer zeroes out the memory that it
 allocates.
 
-Support for dithering was removed by default, because it has never
-been well tested and doesn't work very well.  The code has not
-been removed, however, and can be enabled by building libpng with
-PNG_READ_DITHER_SUPPORTED defined.
+Support for dithering was disabled by default in libpng-1.4.0, because
+been well tested and doesn't actually "dither".  The code was not
+removed, however, and could be enabled by building libpng with
+PNG_READ_DITHER_SUPPORTED defined.  In libpng-1.4.2, this support
+was reenabled, but the function was renamed png_set_quantize() to
+reflect more accurately what it actually does.  At the same time,
+the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
+PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
 
 We removed the trailing '.' from the warning and error messages.
 
@@ -4052,7 +4090,7 @@
 
 .SH XIII. Y2K Compliance in libpng
 
-April 14, 2010
+April 17, 2010
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
@@ -4292,7 +4330,7 @@
 
 Thanks to Frank J. T. Wojcik for helping with the documentation.
 
-Libpng version 1.5.0beta17 - April 14, 2010:
+Libpng version 1.5.0beta17 - April 17, 2010:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
 
@@ -4315,7 +4353,7 @@
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.0beta17, April 14, 2010, are
+libpng versions 1.2.6, August 15, 2004, through 1.5.0beta17, April 17, 2010, are
 Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.2.5
 with the following individual added to the list of Contributing Authors
@@ -4414,7 +4452,7 @@
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-April 14, 2010
+April 17, 2010
 
 .\" end of man page
 
diff --git a/libpngpf.3 b/libpngpf.3
index 0933fdf..0787d99 100644
--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,4 +1,4 @@
-.TH LIBPNGPF 3 "April 1, 2010"
+.TH LIBPNGPF 3 "April 17, 2010"
 .SH NAME
 libpng \- Portable Network Graphics (PNG) Reference Library 1.5.0beta17
 (private functions)
@@ -143,14 +143,6 @@
 
 \fI\fB
 
-\fI\fB
-
-\fBvoid png_do_dither (png_row_infop \fP\fIrow_info\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fP\fIpalette_lookup\fP\fB, png_bytep \fIdither_lookup\fP\fB);\fP
-
-\fI\fB
-
-\fI\fB
-
 \fBvoid png_do_expand (png_row_infop \fP\fIrow_info\fP\fB, png_bytep \fP\fIrow\fP\fB, png_color_16p \fItrans_value\fP\fB);\fP
 
 \fI\fB
@@ -193,6 +185,14 @@
 
 \fI\fB
 
+\fBvoid png_do_quantize (png_row_infop \fP\fIrow_info\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fP\fIpalette_lookup\fP\fB, png_bytep \fIquantize_lookup\fP\fB);\fP
+
+\fI\fB
+
+\fI\fB
+
+\fI\fB
+
 \fBvoid png_do_read_filler (png_row_infop \fP\fIrow_info\fP\fB, png_bytep \fP\fIrow\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, png_uint_32 \fIflags\fP\fB);\fP
 
 \fI\fB
diff --git a/png.5 b/png.5
index eb0daba..f7d4ce3 100644
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "April 1, 2010"
+.TH PNG 5 "April 17, 2010"
 .SH NAME
 png \- Portable Network Graphics (PNG) format
 .SH DESCRIPTION
diff --git a/png.c b/png.c
index 4dd64bb..6aa8452 100644
--- a/png.c
+++ b/png.c
@@ -1,7 +1,7 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
@@ -548,13 +548,13 @@
 #else
 #  ifdef __STDC__
    return ((png_charp) PNG_STRING_NEWLINE \
-     "libpng version 1.5.0beta17 - April 1, 2010" PNG_STRING_NEWLINE \
+     "libpng version 1.5.0beta17 - April 17, 2010" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2010 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 ((png_charp) "libpng version 1.5.0beta17 - April 1, 2010\
+      return ((png_charp) "libpng version 1.5.0beta17 - April 17, 2010\
       Copyright (c) 1998-2010 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.");
diff --git a/png.h b/png.h
index f81780e..2e891ed 100644
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.5.0beta17 - April 1, 2010
+ * libpng version 1.5.0beta17 - April 17, 2010
  * Copyright (c) 1998-2010 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.)
@@ -11,7 +11,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.5.0beta17 - April 1, 2010: Glenn
+ *   libpng versions 0.97, January 1998, through 1.5.0beta17 - April 17, 2010: Glenn
  *   See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -170,7 +170,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.5.0beta17, April 1, 2010, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.5.0beta17, April 17, 2010, are
  * Copyright (c) 2004, 2006-2010 Glenn Randers-Pehrson, and are
  * distributed according to the same disclaimer and license as libpng-1.2.5
  * with the following individual added to the list of Contributing Authors:
@@ -282,7 +282,7 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    April 1, 2010
+ *    April 17, 2010
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
@@ -346,7 +346,7 @@
 /* Version information for png.h - this should match the version in png.c */
 #define PNG_LIBPNG_VER_STRING "1.5.0beta17"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.5.0beta17 - April 1, 2010\n"
+     " libpng version 1.5.0beta17 - April 17, 2010\n"
 
 #define PNG_LIBPNG_VER_SONUM   15
 #define PNG_LIBPNG_VER_DLLNUM  15
@@ -1033,13 +1033,13 @@
 extern PNG_EXPORT(void,png_set_strip_16,(png_structp png_ptr),,48);
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-/* Turn on dithering, and reduce the palette to the number of colors
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+/* Turn on quantizing, and reduce the palette to the number of colors
  * available.
  */
-extern PNG_EXPORT(void,png_set_dither,(png_structp png_ptr,
+extern PNG_EXPORT(void,png_set_quantize,(png_structp png_ptr,
     png_colorp palette, int num_palette, int maximum_colors,
-    png_uint_16p histogram, int full_dither),,49);
+    png_uint_16p histogram, int full_quantize),,49);
 #endif
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
diff --git a/pngconf.h b/pngconf.h
index e7479ad..37d1a3f 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.5.0beta17 - April 1, 2010
+ * libpng version 1.5.0beta17 - April 17, 2010
  *
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -523,18 +523,18 @@
 
 /* Other defines for things like memory and the like can go here.  */
 
-/* This controls how fine the dithering gets.  As this allocates
+/* This controls how fine the quantizing gets.  As this allocates
  * a largish chunk of memory (32K), those who are not as concerned
- * with dithering quality can decrease some or all of these.
+ * with quantizing quality can decrease some or all of these.
  */
-#ifndef PNG_DITHER_RED_BITS
-#  define PNG_DITHER_RED_BITS 5
+#ifndef PNG_QUANTIZE_RED_BITS
+#  define PNG_QUANTIZE_RED_BITS 5
 #endif
-#ifndef PNG_DITHER_GREEN_BITS
-#  define PNG_DITHER_GREEN_BITS 5
+#ifndef PNG_QUANTIZE_GREEN_BITS
+#  define PNG_QUANTIZE_GREEN_BITS 5
 #endif
-#ifndef PNG_DITHER_BLUE_BITS
-#  define PNG_DITHER_BLUE_BITS 5
+#ifndef PNG_QUANTIZE_BLUE_BITS
+#  define PNG_QUANTIZE_BLUE_BITS 5
 #endif
 
 /* This controls how fine the gamma correction becomes when you
@@ -629,6 +629,9 @@
 #    ifndef PNG_NO_READ_INVERT
 #      define PNG_READ_INVERT_SUPPORTED
 #    endif
+#  ifndef PNG_NO_READ_QUANTIZE
+#    define PNG_READ_QUANTIZE_SUPPORTED
+#  endif
 #    ifndef PNG_NO_READ_BACKGROUND
 #      define PNG_READ_BACKGROUND_SUPPORTED
 #    endif
diff --git a/pngdebug.h b/pngdebug.h
index 2b34eae..f76778d 100644
--- a/pngdebug.h
+++ b/pngdebug.h
@@ -5,7 +5,7 @@
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
- * Last changed in libpng version 1.5.0 - April 1, 2010
+ * Last changed in libpng version 1.5.0 - April 17, 2010
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/pngerror.c b/pngerror.c
index cf444b4..8e0569e 100644
--- a/pngerror.c
+++ b/pngerror.c
@@ -1,7 +1,7 @@
 
 /* pngerror.c - stub functions for i/o and memory allocation
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngget.c b/pngget.c
index c367627..08839df 100644
--- a/pngget.c
+++ b/pngget.c
@@ -1,7 +1,7 @@
 
 /* pngget.c - retrieval of values from info struct
  *
- * Last changed in libpng 1.4.1 [April 1, 2010]
+ * Last changed in libpng 1.4.1 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pnginfo.h b/pnginfo.h
index ff07153..c2b31a5 100644
--- a/pnginfo.h
+++ b/pnginfo.h
@@ -5,7 +5,7 @@
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
- * Last changed in libpng version 1.5.0 - April 1, 2010
+ * Last changed in libpng version 1.5.0 - April 17, 2010
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/pngmem.c b/pngmem.c
index b1c0d93..c61fd8b 100644
--- a/pngmem.c
+++ b/pngmem.c
@@ -1,7 +1,7 @@
 
 /* pngmem.c - stub functions for memory allocation
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngpread.c b/pngpread.c
index fb78446..6a03c9c 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -1,7 +1,7 @@
 
 /* pngpread.c - read a png file in push mode
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngpriv.h b/pngpriv.h
index 921467b..ccd6aba 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1,7 +1,7 @@
 
 /* pngpriv.h - private declarations for use inside libpng
  *
- * libpng version 1.5.0beta17 - April 1, 2010
+ * libpng version 1.5.0beta17 - April 17, 2010
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -117,7 +117,7 @@
 #define PNG_SHIFT               0x0008
 #define PNG_SWAP_BYTES          0x0010
 #define PNG_INVERT_MONO         0x0020
-#define PNG_DITHER              0x0040
+#define PNG_QUANTIZE            0x0040
 #define PNG_BACKGROUND          0x0080
 #define PNG_BACKGROUND_EXPAND   0x0100
                           /*    0x0200 unused */
@@ -601,9 +601,9 @@
 PNG_EXTERN void png_do_chop PNGARG((png_row_infop row_info, png_bytep row));
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-PNG_EXTERN void png_do_dither PNGARG((png_row_infop row_info,
-    png_bytep row, png_bytep palette_lookup, png_bytep dither_lookup));
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+PNG_EXTERN void png_do_quantize PNGARG((png_row_infop row_info,
+    png_bytep row, png_bytep palette_lookup, png_bytep quantize_lookup));
 
 #  ifdef PNG_CORRECT_PALETTE_SUPPORTED
 PNG_EXTERN void png_correct_palette PNGARG((png_structp png_ptr,
diff --git a/pngread.c b/pngread.c
index bb0fc3a..f6b956e 100644
--- a/pngread.c
+++ b/pngread.c
@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
@@ -1076,9 +1076,9 @@
    png_free(png_ptr, png_ptr->big_row_buf);
    png_free(png_ptr, png_ptr->prev_row);
    png_free(png_ptr, png_ptr->chunkdata);
-#ifdef PNG_READ_DITHER_SUPPORTED
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
    png_free(png_ptr, png_ptr->palette_lookup);
-   png_free(png_ptr, png_ptr->dither_index);
+   png_free(png_ptr, png_ptr->quantize_index);
 #endif
 #ifdef PNG_READ_GAMMA_SUPPORTED
    png_free(png_ptr, png_ptr->gamma_table);
@@ -1253,7 +1253,7 @@
          png_set_expand(png_ptr);
 #endif
 
-   /* We don't handle background color or gamma transformation or dithering.
+   /* We don't handle background color or gamma transformation or quantizing.
     */
 
 #ifdef PNG_READ_INVERT_SUPPORTED
diff --git a/pngrio.c b/pngrio.c
index 555dcfe..1c793fc 100644
--- a/pngrio.c
+++ b/pngrio.c
@@ -1,7 +1,7 @@
 
 /* pngrio.c - functions for data input
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngrtran.c b/pngrtran.c
index 8133947..dd0cf3a 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 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
@@ -140,13 +140,13 @@
 }
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
 /* Dither file to 8 bit.  Supply a palette, the current number
  * of elements in the palette, the maximum number of elements
  * allowed, and a histogram if possible.  If the current number
  * of colors is greater then the maximum number, the palette will be
- * modified to fit in the maximum number.  "full_dither" indicates
- * whether we need a dithering cube set up for RGB images, or if we
+ * modified to fit in the maximum number.  "full_quantize" indicates
+ * whether we need a quantizing cube set up for RGB images, or if we
  * simply are reducing the number of colors in a paletted image.
  */
 
@@ -160,24 +160,24 @@
 typedef png_dsort FAR * FAR * png_dsortpp;
 
 void PNGAPI
-png_set_dither(png_structp png_ptr, png_colorp palette,
+png_set_quantize(png_structp png_ptr, png_colorp palette,
     int num_palette, int maximum_colors, png_uint_16p histogram,
-    int full_dither)
+    int full_quantize)
 {
-   png_debug(1, "in png_set_dither");
+   png_debug(1, "in png_set_quantize");
 
    if (png_ptr == NULL)
       return;
-   png_ptr->transformations |= PNG_DITHER;
+   png_ptr->transformations |= PNG_QUANTIZE;
 
-   if (!full_dither)
+   if (!full_quantize)
    {
       int i;
 
-      png_ptr->dither_index = (png_bytep)png_malloc(png_ptr,
+      png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
           (png_uint_32)(num_palette * png_sizeof(png_byte)));
       for (i = 0; i < num_palette; i++)
-         png_ptr->dither_index[i] = (png_byte)i;
+         png_ptr->quantize_index[i] = (png_byte)i;
    }
 
    if (num_palette > maximum_colors)
@@ -191,12 +191,12 @@
          int i;
 
          /* Initialize an array to sort colors */
-         png_ptr->dither_sort = (png_bytep)png_malloc(png_ptr,
+         png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
              (png_uint_32)(num_palette * png_sizeof(png_byte)));
 
-         /* Initialize the dither_sort array */
+         /* Initialize the quantize_sort array */
          for (i = 0; i < num_palette; i++)
-            png_ptr->dither_sort[i] = (png_byte)i;
+            png_ptr->quantize_sort[i] = (png_byte)i;
 
          /* Find the least used palette entries by starting a
           * bubble sort, and running it until we have sorted
@@ -213,14 +213,14 @@
             done = 1;
             for (j = 0; j < i; j++)
             {
-               if (histogram[png_ptr->dither_sort[j]]
-                   < histogram[png_ptr->dither_sort[j + 1]])
+               if (histogram[png_ptr->quantize_sort[j]]
+                   < histogram[png_ptr->quantize_sort[j + 1]])
                {
                   png_byte t;
 
-                  t = png_ptr->dither_sort[j];
-                  png_ptr->dither_sort[j] = png_ptr->dither_sort[j + 1];
-                  png_ptr->dither_sort[j + 1] = t;
+                  t = png_ptr->quantize_sort[j];
+                  png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
+                  png_ptr->quantize_sort[j + 1] = t;
                   done = 0;
                }
             }
@@ -229,7 +229,7 @@
          }
 
          /* Swap the palette around, and set up a table, if necessary */
-         if (full_dither)
+         if (full_quantize)
          {
             int j = num_palette;
 
@@ -238,11 +238,11 @@
              */
             for (i = 0; i < maximum_colors; i++)
             {
-               if ((int)png_ptr->dither_sort[i] >= maximum_colors)
+               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
                {
                   do
                      j--;
-                  while ((int)png_ptr->dither_sort[j] >= maximum_colors);
+                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
                   palette[i] = palette[j];
                }
             }
@@ -257,32 +257,32 @@
             for (i = 0; i < maximum_colors; i++)
             {
                /* Only move the colors we need to */
-               if ((int)png_ptr->dither_sort[i] >= maximum_colors)
+               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
                {
                   png_color tmp_color;
 
                   do
                      j--;
-                  while ((int)png_ptr->dither_sort[j] >= maximum_colors);
+                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
 
                   tmp_color = palette[j];
                   palette[j] = palette[i];
                   palette[i] = tmp_color;
                   /* Indicate where the color went */
-                  png_ptr->dither_index[j] = (png_byte)i;
-                  png_ptr->dither_index[i] = (png_byte)j;
+                  png_ptr->quantize_index[j] = (png_byte)i;
+                  png_ptr->quantize_index[i] = (png_byte)j;
                }
             }
 
             /* Find closest color for those colors we are not using */
             for (i = 0; i < num_palette; i++)
             {
-               if ((int)png_ptr->dither_index[i] >= maximum_colors)
+               if ((int)png_ptr->quantize_index[i] >= maximum_colors)
                {
                   int min_d, k, min_k, d_index;
 
                   /* Find the closest color to one we threw out */
-                  d_index = png_ptr->dither_index[i];
+                  d_index = png_ptr->quantize_index[i];
                   min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
                   for (k = 1, min_k = 0; k < maximum_colors; k++)
                   {
@@ -297,12 +297,12 @@
                      }
                   }
                   /* Point to closest color */
-                  png_ptr->dither_index[i] = (png_byte)min_k;
+                  png_ptr->quantize_index[i] = (png_byte)min_k;
                }
             }
          }
-         png_free(png_ptr, png_ptr->dither_sort);
-         png_ptr->dither_sort = NULL;
+         png_free(png_ptr, png_ptr->quantize_sort);
+         png_ptr->quantize_sort = NULL;
       }
       else
       {
@@ -409,19 +409,19 @@
                         num_new_palette--;
                         palette[png_ptr->index_to_palette[j]]
                             = palette[num_new_palette];
-                        if (!full_dither)
+                        if (!full_quantize)
                         {
                            int k;
 
                            for (k = 0; k < num_palette; k++)
                            {
-                              if (png_ptr->dither_index[k] ==
+                              if (png_ptr->quantize_index[k] ==
                                   png_ptr->index_to_palette[j])
-                                 png_ptr->dither_index[k] =
+                                 png_ptr->quantize_index[k] =
                                      png_ptr->index_to_palette[next_j];
-                              if ((int)png_ptr->dither_index[k] ==
+                              if ((int)png_ptr->quantize_index[k] ==
                                   num_new_palette)
-                                 png_ptr->dither_index[k] =
+                                 png_ptr->quantize_index[k] =
                                      png_ptr->index_to_palette[j];
                            }
                         }
@@ -474,15 +474,15 @@
    }
    png_ptr->num_palette = (png_uint_16)num_palette;
 
-   if (full_dither)
+   if (full_quantize)
    {
       int i;
       png_bytep distance;
-      int total_bits = PNG_DITHER_RED_BITS + PNG_DITHER_GREEN_BITS +
-          PNG_DITHER_BLUE_BITS;
-      int num_red = (1 << PNG_DITHER_RED_BITS);
-      int num_green = (1 << PNG_DITHER_GREEN_BITS);
-      int num_blue = (1 << PNG_DITHER_BLUE_BITS);
+      int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
+          PNG_QUANTIZE_BLUE_BITS;
+      int num_red = (1 << PNG_QUANTIZE_RED_BITS);
+      int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
+      int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
       png_size_t num_entries = ((png_size_t)1 << total_bits);
 
       png_ptr->palette_lookup = (png_bytep )png_calloc(png_ptr,
@@ -495,16 +495,16 @@
       for (i = 0; i < num_palette; i++)
       {
          int ir, ig, ib;
-         int r = (palette[i].red >> (8 - PNG_DITHER_RED_BITS));
-         int g = (palette[i].green >> (8 - PNG_DITHER_GREEN_BITS));
-         int b = (palette[i].blue >> (8 - PNG_DITHER_BLUE_BITS));
+         int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
+         int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
+         int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
 
          for (ir = 0; ir < num_red; ir++)
          {
             /* int dr = abs(ir - r); */
             int dr = ((ir > r) ? ir - r : r - ir);
-            int index_r = (ir << (PNG_DITHER_BLUE_BITS +
-                PNG_DITHER_GREEN_BITS));
+            int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
+                PNG_QUANTIZE_GREEN_BITS));
 
             for (ig = 0; ig < num_green; ig++)
             {
@@ -512,7 +512,7 @@
                int dg = ((ig > g) ? ig - g : g - ig);
                int dt = dr + dg;
                int dm = ((dr > dg) ? dr : dg);
-               int index_g = index_r | (ig << PNG_DITHER_BLUE_BITS);
+               int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
 
                for (ib = 0; ib < num_blue; ib++)
                {
@@ -535,7 +535,7 @@
       png_free(png_ptr, distance);
    }
 }
-#endif /* PNG_READ_DITHER_SUPPORTED */
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
 
 #if defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
 /* Transform the image from the file_gamma to the screen_gamma.  We
@@ -1233,8 +1233,8 @@
       info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   if (png_ptr->transformations & PNG_DITHER)
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   if (png_ptr->transformations & PNG_QUANTIZE)
    {
       if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
           (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
@@ -1455,15 +1455,15 @@
       png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   if (png_ptr->transformations & PNG_DITHER)
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   if (png_ptr->transformations & PNG_QUANTIZE)
    {
-      png_do_dither((png_row_infop)&(png_ptr->row_info), png_ptr->row_buf + 1,
-          png_ptr->palette_lookup, png_ptr->dither_index);
+      png_do_quantize((png_row_infop)&(png_ptr->row_info), png_ptr->row_buf + 1,
+          png_ptr->palette_lookup, png_ptr->quantize_index);
       if (png_ptr->row_info.rowbytes == (png_uint_32)0)
-         png_error(png_ptr, "png_do_dither returned rowbytes=0");
+         png_error(png_ptr, "png_do_quantize returned rowbytes=0");
    }
-#endif
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
 
 #ifdef PNG_READ_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
@@ -3808,16 +3808,16 @@
 }
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
 void /* PRIVATE */
-png_do_dither(png_row_infop row_info, png_bytep row,
-    png_bytep palette_lookup, png_bytep dither_lookup)
+png_do_quantize(png_row_infop row_info, png_bytep row,
+    png_bytep palette_lookup, png_bytep quantize_lookup)
 {
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
 
-   png_debug(1, "in png_do_dither");
+   png_debug(1, "in png_do_quantize");
 
    {
       if (row_info->color_type == PNG_COLOR_TYPE_RGB &&
@@ -3839,14 +3839,14 @@
              *    (((g >> 3) & 0x1f) << 5) |
              *    ((b >> 3) & 0x1f);
              */
-            p = (((r >> (8 - PNG_DITHER_RED_BITS)) &
-                ((1 << PNG_DITHER_RED_BITS) - 1)) <<
-                (PNG_DITHER_GREEN_BITS + PNG_DITHER_BLUE_BITS)) |
-                (((g >> (8 - PNG_DITHER_GREEN_BITS)) &
-                ((1 << PNG_DITHER_GREEN_BITS) - 1)) <<
-                (PNG_DITHER_BLUE_BITS)) |
-                ((b >> (8 - PNG_DITHER_BLUE_BITS)) &
-                ((1 << PNG_DITHER_BLUE_BITS) - 1));
+            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+                (PNG_QUANTIZE_BLUE_BITS)) |
+                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
 
             *dp++ = palette_lookup[p];
          }
@@ -3868,14 +3868,14 @@
             b = *sp++;
             sp++;
 
-            p = (((r >> (8 - PNG_DITHER_RED_BITS)) &
-                ((1 << PNG_DITHER_RED_BITS) - 1)) <<
-                (PNG_DITHER_GREEN_BITS + PNG_DITHER_BLUE_BITS)) |
-                (((g >> (8 - PNG_DITHER_GREEN_BITS)) &
-                ((1 << PNG_DITHER_GREEN_BITS) - 1)) <<
-                (PNG_DITHER_BLUE_BITS)) |
-                ((b >> (8 - PNG_DITHER_BLUE_BITS)) &
-                ((1 << PNG_DITHER_BLUE_BITS) - 1));
+            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+                (PNG_QUANTIZE_BLUE_BITS)) |
+                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
 
             *dp++ = palette_lookup[p];
          }
@@ -3885,17 +3885,17 @@
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
       }
       else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
-         dither_lookup && row_info->bit_depth == 8)
+         quantize_lookup && row_info->bit_depth == 8)
       {
          sp = row;
          for (i = 0; i < row_width; i++, sp++)
          {
-            *sp = dither_lookup[*sp];
+            *sp = quantize_lookup[*sp];
          }
       }
    }
 }
-#endif
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
 
 #ifdef PNG_FLOATING_POINT_SUPPORTED
 #ifdef PNG_READ_GAMMA_SUPPORTED
diff --git a/pngrutil.c b/pngrutil.c
index 72bd01a..cc06fb3 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,7 +1,7 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.4.1 [April 1, 2010]
+ * Last changed in libpng 1.4.1 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
@@ -904,9 +904,11 @@
                 green_x, green_y, blue_x, blue_y);
 #else
             fprintf(stderr, "wx=%ld, wy=%ld, rx=%ld, ry=%ld\n",
-                int_x_white, int_y_white, int_x_red, int_y_red);
+               (long)int_x_white, (long)int_y_white,
+               (long)int_x_red, (long)int_y_red);
             fprintf(stderr, "gx=%ld, gy=%ld, bx=%ld, by=%ld\n",
-                int_x_green, int_y_green, int_x_blue, int_y_blue);
+               (long)int_x_green, (long)int_y_green,
+               (long)int_x_blue, (long)int_y_blue);
 #endif
 #endif /* PNG_CONSOLE_IO_SUPPORTED */
          }
diff --git a/pngset.c b/pngset.c
index cde867b..439d049 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1,7 +1,7 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngstruct.h b/pngstruct.h
index 1137d1b..9a704b9 100644
--- a/pngstruct.h
+++ b/pngstruct.h
@@ -5,7 +5,7 @@
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
- * Last changed in libpng version 1.5.0 - April 1, 2010
+ * Last changed in libpng version 1.5.0 - April 17, 2010
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -187,12 +187,12 @@
    png_uint_16 offset_table_count_free;
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   png_bytep palette_lookup; /* lookup table for dithering */
-   png_bytep dither_index;   /* index translation for palette files */
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   png_bytep palette_lookup; /* lookup table for quantizing */
+   png_bytep quantize_index; /* index translation for palette files */
 #endif
 
-#if defined(PNG_READ_DITHER_SUPPORTED) || defined(PNG_hIST_SUPPORTED)
+#if defined(PNG_READ_QUANTIZE_SUPPORTED) || defined(PNG_hIST_SUPPORTED)
    png_uint_16p hist;                /* histogram */
 #endif
 
@@ -263,9 +263,9 @@
 /* New member added in libpng-1.0.13 and 1.2.0 */
    png_bytep big_row_buf;         /* buffer to save current (unfiltered) row */
 
-#ifdef PNG_READ_DITHER_SUPPORTED
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
 /* The following three members were added at version 1.0.14 and 1.2.4 */
-   png_bytep dither_sort;            /* working sort array */
+   png_bytep quantize_sort;          /* working sort array */
    png_bytep index_to_palette;       /* where the original index currently is
                                         in the palette */
    png_bytep palette_to_index;       /* which original index points to this
diff --git a/pngtest.c b/pngtest.c
index b881088..9a3acfe 100644
--- a/pngtest.c
+++ b/pngtest.c
@@ -1,7 +1,7 @@
 
 /* pngtest.c - a simple test program to test libpng
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngtrans.c b/pngtrans.c
index 2c2fef0..4c88cc4 100644
--- a/pngtrans.c
+++ b/pngtrans.c
@@ -1,7 +1,7 @@
 
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngwio.c b/pngwio.c
index b7735f3..65d66fd 100644
--- a/pngwio.c
+++ b/pngwio.c
@@ -1,7 +1,7 @@
 
 /* pngwio.c - functions for data output
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngwrite.c b/pngwrite.c
index 5bffe9c..f6e17f2 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,7 +1,7 @@
 
 /* pngwrite.c - general routines to write a PNG file
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngwtran.c b/pngwtran.c
index a4a791d..9acd331 100644
--- a/pngwtran.c
+++ b/pngwtran.c
@@ -1,7 +1,7 @@
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/pngwutil.c b/pngwutil.c
index 1d6c285..257ee48 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,7 +1,7 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 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.)
diff --git a/scripts/README.txt b/scripts/README.txt
index afb4b97..df9b883 100644
--- a/scripts/README.txt
+++ b/scripts/README.txt
@@ -1,5 +1,5 @@
 
-Makefiles for  libpng version 1.5.0beta17 - April 1, 2010
+Makefiles for  libpng version 1.5.0beta17 - April 17, 2010
 
  makefile.linux    =>  Linux/ELF makefile
                        (gcc, creates libpng15.so.15.1.5.0beta17)
diff --git a/scripts/checksym.dfn b/scripts/checksym.dfn
index fe2b63d..39f7e21 100644
--- a/scripts/checksym.dfn
+++ b/scripts/checksym.dfn
@@ -1,7 +1,7 @@
 
 /* pngwin.dfn - find all exported symbols
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  *
  * This code is released under the libpng license.
diff --git a/scripts/symbols.def b/scripts/symbols.def
index 75a4480..f650f72 100644
--- a/scripts/symbols.def
+++ b/scripts/symbols.def
@@ -54,7 +54,7 @@
  png_set_invert_mono @46
  png_set_background @47
  png_set_strip_16 @48
- png_set_dither @49
+; png_set_dither @49
  png_set_gamma @50
  png_set_flush @51
  png_write_flush @52
@@ -213,3 +213,4 @@
  png_save_uint_32 @205
  png_save_int_32 @206
  png_save_uint_16 @207
+ png_set_quantize @208