README - third_party/libpng - Git at Google

 README for libpng 1.00 (shared library 2.1)
 See the note about version numbers near the top of png.h

 See INSTALL for instructions on how to install libpng.

 This is the first official release of libpng.  Don't let the fact that
 it's the first release fool you.  The libpng library has been in
 extensive use and testing for about two and a half years.  However, it's
 finally gotten to the stage where there haven't been significant
 changes to the API in some time, and people have a bad feeling about
 libraries with versions < 1.0.

 ****
 Note that some of the changes to the png_info structure render this
 version of the library binary incompatible with libpng-0.89 or
 earlier versions if you are using a shared library.  The type of the
 "filler" parameter for png_set_filler() has changed from png_byte to
 png_uint_32, which will affect shared-library applications that use
 this function.

 To avoid problems with changes to the internals of png_info_struct,
 new APIs have been made available in 0.95 to avoid direct application
 access to info_ptr.  These functions are the png_set_<chunk> and
 png_get_<chunk> functions.  These functions should be used when
 accessing/storing the info_struct data, rather than manipulating it
 directly, to avoid such problems in the future.

 It is important to note that the APIs do not make current programs
 that access the info struct directly incompatible with the new
 library.  However, it is strongly suggested that new programs use
 the new APIs (as shown in example.c), and older programs be converted
 to the new format, to facilitate upgrades in the future.
 ****

 Additions since 0.90 include the ability to compile libpng as a
 Windows DLL, and new APIs for accessing data in the info struct.
 Experimental functions include the ability to set weighting and cost
 factors for row filter selection, direct reads of integers from buffers
 on big-endian processors that support misaligned data access, faster
 methods of doing alpha composition, and more accurate 16->8 bit color
 conversion.

 The additions since 0.89 include the ability to read from a PNG stream
 which has had some (or all) of the signature bytes read by the calling
 application.  This also allows the reading of embedded PNG streams that
 do not have the PNG file signature.  As well, it is now possible to set
 the library action on the detection of chunk CRC errors.  It is possible
 to set different actions based on whether the CRC error occurred in a
 critical or an ancillary chunk.

 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
 examples of libpng in a program, see example.c and pngtest.c.  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 should use zlib 1.0.4 or later to run this, but it MAY work with
 versions as old as zlib 0.95.  Even so, there are bugs in older zlib
 versions which can cause the output of invalid compression streams for
 some images.  You will definitely need zlib 1.0.4 or later if you are
 taking advantage of the MS-DOS "far" structure allocation for the small
 and medium memory models.  You should also note that zlib is a
 compression library that is useful for more things than just PNG files.
 You can use zlib as a drop-in replacement for fread() and fwrite() if
 you are so inclined.

 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 is available
 as an RFC and a W3C Recommendation.  Failing
 these resources you can 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 (of course
 based in a large way on Guy's and Andreas' earlier work), and the PNG group.

 randeg@alumni.rpi.edu
 png-implement@dworkin.wustl.edu

 You can't reach Guy, the original libpng author, at the addresses
 given in previous versions of this document.  He and Andreas will read mail
 addressed to the png-implement list, however.

 Please do not send general questions about PNG.  Send them to
 the address in the specification (png-group@w3.org).  At the same
 time, please do not send libpng questions to that address, send them to me
 or to png-implement@dworkin.wustl.edu.  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 three years 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.

 Files in this distribution:

       CHANGES       =>  Description of changes between libpng versions
       README        =>  This file
       TODO          =>  Things not implemented in the current library
       ansi2knr.1    =>  Manual page for ansi2knr
       ansi2knr.c    =>  Converts files to K&R style function declarations
       build.bat     =>  MS-DOS batch file for Borland compiler
       descrip.mms   =>  VMS project file
       example.c     =>  Example code for using libpng functions
       libpng.3      =>  manual page for libpng
       libpng.txt    =>  Description of libpng and its functions
       libpngpf.3    =>  manual page for libpng's private functions
       png.5         =>  manual page for the PNG format
       png.c         =>  Basic interface functions common to library
       png.h         =>  Library function and interface declarations
       pngconf.h     =>  System specific library configuration
       pngerror.c    =>  Error/warning message I/O functions
       pngget.c      =>  Functions for retrieving info from struct
       pngmem.c      =>  Memory handling functions
       pngpread.c    =>  Progressive reading functions
       pngread.c     =>  Read data/helper high-level functions
       pngrio.c      =>  Lowest-level data read I/O functions
       pngrtran.c    =>  Read data transformation functions
       pngrutil.c    =>  Read data utility functions
       pngset.c      =>  Functions for storing data into the info_struct
       pngtest.c     =>  Library test program
       pngtest.png   =>  Library test sample image
       pngtrans.c    =>  Common data transformation functions
       pngwio.c      =>  Lowest-level write I/O functions
       pngwrite.c    =>  High-level write functions
       pngwtran.c    =>  Write data transformations
       pngwutil.c    =>  Write utility functions
       scripts       =>  Directory containing scripts for building libpng:
         descrip.mms   =>  VMS makefile for MMS or MMK
         makefile.std  =>  Generic UNIX makefile
         makefile.knr  =>  Archaic UNIX Makefile that converts files with ansi2knr
         makefile.dec  =>  DEC Alpha UNIX makefile
         makefile.sgi  =>  Silicon Graphics IRIX makefile
         makefile.sun  =>  Sun makefile
         makefile.s2x  =>  Solaris 2.X makefile (gcc, creates libpng.so.2.1.00)
         makefile.lnx  =>  Linux/ELF makefile (gcc, creates libpng.so.2.1.00)
         makefile.mip  =>  MIPS makefile
         makefile.aco  =>  Acorn makefile
         makefile.ama  =>  Amiga makefile
         makefile.atr  =>  Atari makefile
         makefile.bor  =>  Borland makefile
         build.bat     =>  MS-DOS batch file for Borland compiler
         makefile.dj2  =>  DJGPP 2 makefile
         makefile.msc  =>  Microsoft C makefile
         makefile.tc3  =>  Turbo C 3.0 makefile
         makefile.os2  =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
         makefile.wat  =>  Watcom 10a+ Makefile, 32-bit flat memory model
         pngos2.def    =>  OS/2 module definition file used by makefile.os2
         makevms.com   =>  VMS build script

 Good luck, and happy coding.

 -Glenn Randers-Pehrson
  Internet: randeg@alumni.rpi.edu
  Web: http://www.rpi.edu/~randeg/index.html

 -Andreas Eric Dilger
  Internet: adilger@enel.ucalgary.ca
  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/

 -Guy Eric Schalnat
  (formerly of Group 42, Inc)
  Internet: gschal@infinet.com
	README for libpng 1.00 (shared library 2.1)
	See the note about version numbers near the top of png.h

	See INSTALL for instructions on how to install libpng.

	This is the first official release of libpng. Don't let the fact that
	it's the first release fool you. The libpng library has been in
	extensive use and testing for about two and a half years. However, it's
	finally gotten to the stage where there haven't been significant
	changes to the API in some time, and people have a bad feeling about
	libraries with versions < 1.0.

	****
	Note that some of the changes to the png_info structure render this
	version of the library binary incompatible with libpng-0.89 or
	earlier versions if you are using a shared library. The type of the
	"filler" parameter for png_set_filler() has changed from png_byte to
	png_uint_32, which will affect shared-library applications that use
	this function.

	To avoid problems with changes to the internals of png_info_struct,
	new APIs have been made available in 0.95 to avoid direct application
	access to info_ptr. These functions are the png_set_<chunk> and
	png_get_<chunk> functions. These functions should be used when
	accessing/storing the info_struct data, rather than manipulating it
	directly, to avoid such problems in the future.

	It is important to note that the APIs do not make current programs
	that access the info struct directly incompatible with the new
	library. However, it is strongly suggested that new programs use
	the new APIs (as shown in example.c), and older programs be converted
	to the new format, to facilitate upgrades in the future.
	****

	Additions since 0.90 include the ability to compile libpng as a
	Windows DLL, and new APIs for accessing data in the info struct.
	Experimental functions include the ability to set weighting and cost
	factors for row filter selection, direct reads of integers from buffers
	on big-endian processors that support misaligned data access, faster
	methods of doing alpha composition, and more accurate 16->8 bit color
	conversion.

	The additions since 0.89 include the ability to read from a PNG stream
	which has had some (or all) of the signature bytes read by the calling
	application. This also allows the reading of embedded PNG streams that
	do not have the PNG file signature. As well, it is now possible to set
	the library action on the detection of chunk CRC errors. It is possible
	to set different actions based on whether the CRC error occurred in a
	critical or an ancillary chunk.

	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
	examples of libpng in a program, see example.c and pngtest.c. 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 should use zlib 1.0.4 or later to run this, but it MAY work with
	versions as old as zlib 0.95. Even so, there are bugs in older zlib
	versions which can cause the output of invalid compression streams for
	some images. You will definitely need zlib 1.0.4 or later if you are
	taking advantage of the MS-DOS "far" structure allocation for the small
	and medium memory models. You should also note that zlib is a
	compression library that is useful for more things than just PNG files.
	You can use zlib as a drop-in replacement for fread() and fwrite() if
	you are so inclined.

	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 is available
	as an RFC and a W3C Recommendation. Failing
	these resources you can 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 (of course
	based in a large way on Guy's and Andreas' earlier work), and the PNG group.

	randeg@alumni.rpi.edu
	png-implement@dworkin.wustl.edu

	You can't reach Guy, the original libpng author, at the addresses
	given in previous versions of this document. He and Andreas will read mail
	addressed to the png-implement list, however.

	Please do not send general questions about PNG. Send them to
	the address in the specification (png-group@w3.org). At the same
	time, please do not send libpng questions to that address, send them to me
	or to png-implement@dworkin.wustl.edu. 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 three years 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.

	Files in this distribution:

	CHANGES => Description of changes between libpng versions
	README => This file
	TODO => Things not implemented in the current library
	ansi2knr.1 => Manual page for ansi2knr
	ansi2knr.c => Converts files to K&R style function declarations
	build.bat => MS-DOS batch file for Borland compiler
	descrip.mms => VMS project file
	example.c => Example code for using libpng functions
	libpng.3 => manual page for libpng
	libpng.txt => Description of libpng and its functions
	libpngpf.3 => manual page for libpng's private functions
	png.5 => manual page for the PNG format
	png.c => Basic interface functions common to library
	png.h => Library function and interface declarations
	pngconf.h => System specific library configuration
	pngerror.c => Error/warning message I/O functions
	pngget.c => Functions for retrieving info from struct
	pngmem.c => Memory handling functions
	pngpread.c => Progressive reading functions
	pngread.c => Read data/helper high-level functions
	pngrio.c => Lowest-level data read I/O functions
	pngrtran.c => Read data transformation functions
	pngrutil.c => Read data utility functions
	pngset.c => Functions for storing data into the info_struct
	pngtest.c => Library test program
	pngtest.png => Library test sample image
	pngtrans.c => Common data transformation functions
	pngwio.c => Lowest-level write I/O functions
	pngwrite.c => High-level write functions
	pngwtran.c => Write data transformations
	pngwutil.c => Write utility functions
	scripts => Directory containing scripts for building libpng:
	descrip.mms => VMS makefile for MMS or MMK
	makefile.std => Generic UNIX makefile
	makefile.knr => Archaic UNIX Makefile that converts files with ansi2knr
	makefile.dec => DEC Alpha UNIX makefile
	makefile.sgi => Silicon Graphics IRIX makefile
	makefile.sun => Sun makefile
	makefile.s2x => Solaris 2.X makefile (gcc, creates libpng.so.2.1.00)
	makefile.lnx => Linux/ELF makefile (gcc, creates libpng.so.2.1.00)
	makefile.mip => MIPS makefile
	makefile.aco => Acorn makefile
	makefile.ama => Amiga makefile
	makefile.atr => Atari makefile
	makefile.bor => Borland makefile
	build.bat => MS-DOS batch file for Borland compiler
	makefile.dj2 => DJGPP 2 makefile
	makefile.msc => Microsoft C makefile
	makefile.tc3 => Turbo C 3.0 makefile
	makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def)
	makefile.wat => Watcom 10a+ Makefile, 32-bit flat memory model
	pngos2.def => OS/2 module definition file used by makefile.os2
	makevms.com => VMS build script

	Good luck, and happy coding.

	-Glenn Randers-Pehrson
	Internet: randeg@alumni.rpi.edu
	Web: http://www.rpi.edu/~randeg/index.html

	-Andreas Eric Dilger
	Internet: adilger@enel.ucalgary.ca
	Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/

	-Guy Eric Schalnat
	(formerly of Group 42, Inc)
	Internet: gschal@infinet.com