README - third_party/libpng - Git at Google

 			       pngmeta
 			       =======

 This small filter program extracts metadata from PNG images and
 displays them as either HTML, SOIF, RDF/XML or simple fields and
 values.

 This software is distributed under the same copyright as the PNG
 Reference Library (libpng), upon which some of this code is based --
 see pngmeta.c for details.


 Requirements
 ------------

 * An ANSI C compiler -- preferrably gcc
 * libpng (tested with 1.0.0, 1.0.03)
 * zlib   (tested with 1.1.1, 1.1.3)

 The latter two packages are available from ftp://ftp.uu.net/graphics/png/
 andr many other places, see the PNG Home Page for details.


 Installation
 ------------

 Use the GNU configuration program:
     ./configure
     make

 This package needs the libpng and zlib libraries and header files and
 you have several ways to specify this if the above fails.

 If you have installed these packages in the default places (libs in
 usual lib path, includes under /usr/include), then they will be
 automatically found.

 If you have compiled the packages but they remain in the source dirs,
 use one of these options to configure:

   --with-png=DIR          DIR is root for libpng distribution
   --with-zlib=DIR         DIR is root for libz distribution

 Note, this automatically happens the distributions are found in
 nearby directories with these names:
   zlib-X.*    zlib   (subdirectories) or ../zlib
   libpng-X.*  libpng (subdirectories) or ../libpng

 If the libraries and headers are installed in places that cannot be
 found by configure, you can specify the individual libraries and
 include paths with these options:

   --with-zlib-lib=LIB     LIB is path to libz.a
   --with-png-lib=LIB      LIB is path to libpng.a
   --with-png-includes=DIR DIR is path where PNG header files can be
                           found, defaults to /usr/include
   --with-zlib-includes=DIR DIR is path where ZLIB header files can be
                            found, defaults to /usr/include


 OR If all of that fails, use the Makefile.old, Edit the ZLIB and
 LIBPNG variables in the makefile to point to the zlib and libpng
 installation directories.  Pick a C compiler (by default set for gcc)
 and ranlib and then do a 'make -f Makefile.old'.


 Testing
 -------

 Three test PNG images are provided:
   ct1n0g04.png ctzn0g04.png
     which contain uncompressed and compressed text chunks respectively.
     These are part of the PNG image test suite written by
     Willem A.J. van Schaik <gwillem@ntuvax.ntu.ac.sg>

   8859.png
     All the printable ISO 8859-1 Latin 1 characters from hex codes
     20 to 7E and A0 to FF provided by Chris Lilley <chris@w3.org>

 and these are all checked when 'make check' is run


 Usage Examples
 --------------

 mint% pngmeta goldhill.png
 pngmeta: PNG meta data for goldhill.png:
 Title: GOLDHILL: Photo of hill in small European town.
 Copyright: Unknown
 Modification Time: 23 Apr 1995 01:15:08 +0000

 mint% pngmeta --soif ct1n0g04.png
 @FILE { ct1n0g04.png
 image-format{3}:	PNG
 image-colors{1}:	4
 image-width{2}:	32
 image-height{2}:	32
 image-type{25}:	Grayscale, non-interlaced
 Title{8}:	PngSuite
 Author{49}:	Willem A.J. van Schaik
 (gwillem@ntuvax.ntu.ac.sg)
 Copyright{43}:	Copyright Willem van Schaik, Singapore 1995
 Description{239}:	A compilation of a set of images created to test the
 various color-types of the PNG format. Included are
 black&white, color, paletted, with alpha channel, with
 transparency formats. All bit-depths allowed according
 to the spec are present.
 Software{48}:	Created on a NeXTstation color using "pnmtopng".
 Disclaimer{9}:	Freeware.
 }


 See the manual page for more information on the options and usage.


 Implementation
 --------------

 The program contains a new function png_skip_till_end() that takes up
 the reading of the PNG data stream after the first IDAT has been
 detected.  It then copies through, checking the CRCs of them but not
 decompressing or processing them.  Finally, any remaining chunks are
 processed in the standard fashion.


 Copyright
 ---------

 This code was modified from the code for png_read_end() from the
 libpng library.  See pngmeta.c for the full copyright headers - they
 have to remain in that file to comply with them.

 The GNU automake/autoconf configuration files and all that libpng and
 zlib searching stuff was written by me and I give permission for
 other people to use it to autoconfigure png and zlib in their
 programs, as long as you acknowledge me.


 Thanks
 ------
 ... to Rick Rodgers <rodgers@nlm.nih.gov> for the manual page.
 ... to Dan Brickley <daniel.brickley@bristol.ac.uk> for the RDF/XML output.


 Dave Beckett
 D.J.Beckett@ukc.ac.uk
 http://www.cs.ukc.ac.uk/people/staff/djb1/
 31st January 2000
	pngmeta
	=======

	This small filter program extracts metadata from PNG images and
	displays them as either HTML, SOIF, RDF/XML or simple fields and
	values.

	This software is distributed under the same copyright as the PNG
	Reference Library (libpng), upon which some of this code is based --
	see pngmeta.c for details.


	Requirements
	------------

	* An ANSI C compiler -- preferrably gcc
	* libpng (tested with 1.0.0, 1.0.03)
	* zlib (tested with 1.1.1, 1.1.3)

	The latter two packages are available from ftp://ftp.uu.net/graphics/png/
	andr many other places, see the PNG Home Page for details.


	Installation
	------------

	Use the GNU configuration program:
	./configure
	make

	This package needs the libpng and zlib libraries and header files and
	you have several ways to specify this if the above fails.

	If you have installed these packages in the default places (libs in
	usual lib path, includes under /usr/include), then they will be
	automatically found.

	If you have compiled the packages but they remain in the source dirs,
	use one of these options to configure:

	--with-png=DIR DIR is root for libpng distribution
	--with-zlib=DIR DIR is root for libz distribution

	Note, this automatically happens the distributions are found in
	nearby directories with these names:
	zlib-X.* zlib (subdirectories) or ../zlib
	libpng-X.* libpng (subdirectories) or ../libpng

	If the libraries and headers are installed in places that cannot be
	found by configure, you can specify the individual libraries and
	include paths with these options:

	--with-zlib-lib=LIB LIB is path to libz.a
	--with-png-lib=LIB LIB is path to libpng.a
	--with-png-includes=DIR DIR is path where PNG header files can be
	found, defaults to /usr/include
	--with-zlib-includes=DIR DIR is path where ZLIB header files can be
	found, defaults to /usr/include




	OR If all of that fails, use the Makefile.old, Edit the ZLIB and
	LIBPNG variables in the makefile to point to the zlib and libpng
	installation directories. Pick a C compiler (by default set for gcc)
	and ranlib and then do a 'make -f Makefile.old'.


	Testing
	-------

	Three test PNG images are provided:
	ct1n0g04.png ctzn0g04.png
	which contain uncompressed and compressed text chunks respectively.
	These are part of the PNG image test suite written by
	Willem A.J. van Schaik <gwillem@ntuvax.ntu.ac.sg>

	8859.png
	All the printable ISO 8859-1 Latin 1 characters from hex codes
	20 to 7E and A0 to FF provided by Chris Lilley <chris@w3.org>

	and these are all checked when 'make check' is run


	Usage Examples
	--------------

	mint% pngmeta goldhill.png
	pngmeta: PNG meta data for goldhill.png:
	Title: GOLDHILL: Photo of hill in small European town.
	Copyright: Unknown
	Modification Time: 23 Apr 1995 01:15:08 +0000

	mint% pngmeta --soif ct1n0g04.png
	@FILE { ct1n0g04.png
	image-format{3}: PNG
	image-colors{1}: 4
	image-width{2}: 32
	image-height{2}: 32
	image-type{25}: Grayscale, non-interlaced
	Title{8}: PngSuite
	Author{49}: Willem A.J. van Schaik
	(gwillem@ntuvax.ntu.ac.sg)
	Copyright{43}: Copyright Willem van Schaik, Singapore 1995
	Description{239}: A compilation of a set of images created to test the
	various color-types of the PNG format. Included are
	black&white, color, paletted, with alpha channel, with
	transparency formats. All bit-depths allowed according
	to the spec are present.
	Software{48}: Created on a NeXTstation color using "pnmtopng".
	Disclaimer{9}: Freeware.
	}


	See the manual page for more information on the options and usage.


	Implementation
	--------------

	The program contains a new function png_skip_till_end() that takes up
	the reading of the PNG data stream after the first IDAT has been
	detected. It then copies through, checking the CRCs of them but not
	decompressing or processing them. Finally, any remaining chunks are
	processed in the standard fashion.


	Copyright
	---------

	This code was modified from the code for png_read_end() from the
	libpng library. See pngmeta.c for the full copyright headers - they
	have to remain in that file to comply with them.

	The GNU automake/autoconf configuration files and all that libpng and
	zlib searching stuff was written by me and I give permission for
	other people to use it to autoconfigure png and zlib in their
	programs, as long as you acknowledge me.


	Thanks
	------
	... to Rick Rodgers <rodgers@nlm.nih.gov> for the manual page.
	... to Dan Brickley <daniel.brickley@bristol.ac.uk> for the RDF/XML output.


	Dave Beckett
	D.J.Beckett@ukc.ac.uk
	http://www.cs.ukc.ac.uk/people/staff/djb1/
	31st January 2000