readme.txt - third_party/libpng - Git at Google

 readme.txt - for libpng 0.89

 This is a bug fix for the third beta version of libpng 1.0.  The
 changes from libpng-0.88 are bug fixes and some changes to the
 API itself to increase robustness with shared libraries.  This
 release is based on libpng-0.88, but has been modified from that
 version by Andreas Dilger <adilger@enel.ucalgary.ca> because the
 original author, Guy Schalnat, has not been able to keep up with
 the time demands of maintaining this library.

 The callback functions for the error/warning messages have changed
 since the last release because their implementation was broken,
 and it was thought best to change the API itself (which was only
 introduced in libpng-0.88 itself) to alert the user to the change,
 rather than mislead the user into thinking their application was
 OK after re-compiling.  This means that calls to png_set_message_fn()
 no longer exist, because the previously suggested method of calling
 them before png_read_init() or png_write_init() is now ineffective.

 The preferred method of setting the error and warning callbacks
 has been incorporated into the allocation of the png_struct and
 info_struct itself, which allow them to be safely used during the
 initialization of the structure, as well as to keep the size of
 the png_struct internal to the library, rather than at compile time
 of the application.  This will hopefully remove any problems with
 dynamically linked libraries, and should be considered the preferred
 method of creating these structures, although the previous
 initialization API is still available for compatibility.  See libpng.txt
 for more information on the new API.

 The changes made to the library, and bugs fixed are based on discussions
 on the PNG implementation mailing list <png-implement@dworking.wustl.edu>
 and not on material submitted to Guy.

 For a detailed description on using libpng, read libpng.txt.  For
 usage information and restrictions (what little they are) on libpng,
 see png.h.  For a description on using zlib (the compression library
 used by libpng) and zlib's restrictions, see zlib.h

 I have included a general makefile, as well as several machine and compiler
 specific ones, but you may have to modify one for your own needs.

 You will need zlib 0.95 or later to run this.  zlib is a compression
 library that is useful for more things then just png files.  If
 you need a compression library, check out zlib.h.  There was a bug in
 zlib <= 0.99 which caused it to generate invalid compression streams
 on some occasions.  Later versions of zlib do not have this problem.

 zlib should be available at the same place that libpng is.
 If not, it should be at ftp.uu.net in /graphics/png
 Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib

 You may also want a copy of the PNG specification.  It should
 be available at the same place you picked up libpng.  If it is
 not there, try ftp.uu.net in the /graphics/png directory.

 This code is currently being archived at ftp.uu.net in the
 /graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT)
 at GO GRAPHSUP.  If you can't find it in any of those places,
 e-mail me, and I'll help you find it.

 If you have any code changes, requests, problems, etc., please e-mail
 them to me.  Also, I'd appreciate any make files or project files,
 and any modifications you needed to make to get libpng to compile,
 along with a #define variable to tell what compiler/system you are on.
 If you needed to add transformations to libpng, or wish libpng would
 provide the image in a different way, drop me a note (and code, if
 possible), so I can consider supporting the transformation.
 Finally, if you get any warning messages when compiling libpng
 (note: not zlib), and they are easy to fix, I'd appreciate the
 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.

 This release was created and will be supported by myself, and the
 PNG group.

 adilger@enel.ucalgary.ca
 png-implement@dworkin.wustl.edu

 You can reach Guy, the original libpng author, at (internet preferred):

 internet: schalnat@group42.com
 CompuServe: 75501,1625

 Please do not send general questions about PNG.  Send them to
 the address in the specification.  At the same time, please do
 not send libpng questions to that address, send them to me.  I'll
 get them in the end anyway.  If you have a question about something
 in the PNG specification that is related to using libpng, send it
 to me.  Send me any questions that start with "I was using libpng,
 and ...".  If in doubt, send questions to me.  I'll bounce them
 to others, if necessary.

 Please do not send suggestions on how to change PNG.  We have
 been discussing PNG for over a year now, and it is official and
 finished.  If you have suggestions for libpng, however, I'll
 gladly listen.  Even if your suggestion is not used for version
 1.0, it may be used later.

 Good luck, and happy coding.

 -Guy Eric Schalnat
  Group 42, Inc.
  Internet: schalnat@group42.com
  CompuServe: 75501,1625
  Web: www.group42.com
	readme.txt - for libpng 0.89

	This is a bug fix for the third beta version of libpng 1.0. The
	changes from libpng-0.88 are bug fixes and some changes to the
	API itself to increase robustness with shared libraries. This
	release is based on libpng-0.88, but has been modified from that
	version by Andreas Dilger <adilger@enel.ucalgary.ca> because the
	original author, Guy Schalnat, has not been able to keep up with
	the time demands of maintaining this library.

	The callback functions for the error/warning messages have changed
	since the last release because their implementation was broken,
	and it was thought best to change the API itself (which was only
	introduced in libpng-0.88 itself) to alert the user to the change,
	rather than mislead the user into thinking their application was
	OK after re-compiling. This means that calls to png_set_message_fn()
	no longer exist, because the previously suggested method of calling
	them before png_read_init() or png_write_init() is now ineffective.

	The preferred method of setting the error and warning callbacks
	has been incorporated into the allocation of the png_struct and
	info_struct itself, which allow them to be safely used during the
	initialization of the structure, as well as to keep the size of
	the png_struct internal to the library, rather than at compile time
	of the application. This will hopefully remove any problems with
	dynamically linked libraries, and should be considered the preferred
	method of creating these structures, although the previous
	initialization API is still available for compatibility. See libpng.txt
	for more information on the new API.

	The changes made to the library, and bugs fixed are based on discussions
	on the PNG implementation mailing list <png-implement@dworking.wustl.edu>
	and not on material submitted to Guy.

	For a detailed description on using libpng, read libpng.txt. For
	usage information and restrictions (what little they are) on libpng,
	see png.h. For a description on using zlib (the compression library
	used by libpng) and zlib's restrictions, see zlib.h

	I have included a general makefile, as well as several machine and compiler
	specific ones, but you may have to modify one for your own needs.

	You will need zlib 0.95 or later to run this. zlib is a compression
	library that is useful for more things then just png files. If
	you need a compression library, check out zlib.h. There was a bug in
	zlib <= 0.99 which caused it to generate invalid compression streams
	on some occasions. Later versions of zlib do not have this problem.

	zlib should be available at the same place that libpng is.
	If not, it should be at ftp.uu.net in /graphics/png
	Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib

	You may also want a copy of the PNG specification. It should
	be available at the same place you picked up libpng. If it is
	not there, try ftp.uu.net in the /graphics/png directory.

	This code is currently being archived at ftp.uu.net in the
	/graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT)
	at GO GRAPHSUP. If you can't find it in any of those places,
	e-mail me, and I'll help you find it.

	If you have any code changes, requests, problems, etc., please e-mail
	them to me. Also, I'd appreciate any make files or project files,
	and any modifications you needed to make to get libpng to compile,
	along with a #define variable to tell what compiler/system you are on.
	If you needed to add transformations to libpng, or wish libpng would
	provide the image in a different way, drop me a note (and code, if
	possible), so I can consider supporting the transformation.
	Finally, if you get any warning messages when compiling libpng
	(note: not zlib), and they are easy to fix, I'd appreciate the
	fix. Please mention "libpng" somewhere in the subject line. Thanks.

	This release was created and will be supported by myself, and the
	PNG group.

	adilger@enel.ucalgary.ca
	png-implement@dworkin.wustl.edu

	You can reach Guy, the original libpng author, at (internet preferred):

	internet: schalnat@group42.com
	CompuServe: 75501,1625

	Please do not send general questions about PNG. Send them to
	the address in the specification. At the same time, please do
	not send libpng questions to that address, send them to me. I'll
	get them in the end anyway. If you have a question about something
	in the PNG specification that is related to using libpng, send it
	to me. Send me any questions that start with "I was using libpng,
	and ...". If in doubt, send questions to me. I'll bounce them
	to others, if necessary.

	Please do not send suggestions on how to change PNG. We have
	been discussing PNG for over a year now, and it is official and
	finished. If you have suggestions for libpng, however, I'll
	gladly listen. Even if your suggestion is not used for version
	1.0, it may be used later.

	Good luck, and happy coding.

	-Guy Eric Schalnat
	Group 42, Inc.
	Internet: schalnat@group42.com
	CompuServe: 75501,1625
	Web: www.group42.com