README for libpng version 1.2.40 - September 10, 2009 (shared library 12.0)+
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See the note about version numbers near the top of png.h+
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+
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See INSTALL for instructions on how to install libpng.+
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+
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Libpng comes in several distribution formats.  Get libpng-*.tar.gz,+
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libpng-*.tar.lzma, or libpng-*.tar.bz2 if you want UNIX-style line+
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endings in the text files, or lpng*.7z or lpng*.zip if you want DOS-style+
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line endings.  You can get UNIX-style line endings from the *.zip file+
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by using "unzip -a" but there seems to be no simple way to recover+
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UNIX-style line endings from the *.7z file.  The *.tar.lzma file is+
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recommended for *NIX users instead.+
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+
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Version 0.89 was the first official release of libpng.  Don't let the+
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fact that it's the first release fool you.  The libpng library has been in+
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extensive use and testing since mid-1995.  By late 1997 it had+
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finally gotten to the stage where there hadn't been significant+
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changes to the API in some time, and people have a bad feeling about+
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libraries with versions < 1.0.  Version 1.0.0 was released in+
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March 1998.+
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+
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****+
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Note that some of the changes to the png_info structure render this+
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version of the library binary incompatible with libpng-0.89 or+
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earlier versions if you are using a shared library.  The type of the+
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"filler" parameter for png_set_filler() has changed from png_byte to+
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png_uint_32, which will affect shared-library applications that use+
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this function.+
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+
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To avoid problems with changes to the internals of png_info_struct,+
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new APIs have been made available in 0.95 to avoid direct application+
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access to info_ptr.  These functions are the png_set_<chunk> and+
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png_get_<chunk> functions.  These functions should be used when+
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accessing/storing the info_struct data, rather than manipulating it+
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directly, to avoid such problems in the future.+
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+
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It is important to note that the APIs do not make current programs+
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that access the info struct directly incompatible with the new+
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library.  However, it is strongly suggested that new programs use+
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the new APIs (as shown in example.c and pngtest.c), and older programs+
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be converted to the new format, to facilitate upgrades in the future.+
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****+
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+
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Additions since 0.90 include the ability to compile libpng as a+
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Windows DLL, and new APIs for accessing data in the info struct.+
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Experimental functions include the ability to set weighting and cost+
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factors for row filter selection, direct reads of integers from buffers+
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on big-endian processors that support misaligned data access, faster+
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methods of doing alpha composition, and more accurate 16->8 bit color+
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conversion.+
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+
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The additions since 0.89 include the ability to read from a PNG stream+
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which has had some (or all) of the signature bytes read by the calling+
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application.  This also allows the reading of embedded PNG streams that+
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do not have the PNG file signature.  As well, it is now possible to set+
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the library action on the detection of chunk CRC errors.  It is possible+
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to set different actions based on whether the CRC error occurred in a+
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critical or an ancillary chunk.+
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+
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The changes made to the library, and bugs fixed are based on discussions+
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on the png-mng-implement mailing list+
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and not on material submitted privately to Guy, Andreas, or Glenn.  They will+
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forward any good suggestions to the list.+
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+
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For a detailed description on using libpng, read libpng.txt.  For+
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examples of libpng in a program, see example.c and pngtest.c.  For usage+
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information and restrictions (what little they are) on libpng, see+
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png.h.  For a description on using zlib (the compression library used by+
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libpng) and zlib's restrictions, see zlib.h+
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+
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I have included a general makefile, as well as several machine and+
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compiler specific ones, but you may have to modify one for your own needs.+
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+
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You should use zlib 1.0.4 or later to run this, but it MAY work with+
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versions as old as zlib 0.95.  Even so, there are bugs in older zlib+
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versions which can cause the output of invalid compression streams for+
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some images.  You will definitely need zlib 1.0.4 or later if you are+
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taking advantage of the MS-DOS "far" structure allocation for the small+
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and medium memory models.  You should also note that zlib is a+
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compression library that is useful for more things than just PNG files.+
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You can use zlib as a drop-in replacement for fread() and fwrite() if+
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you are so inclined.+
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+
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zlib should be available at the same place that libpng is, or at+
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ftp://ftp.simplesystems.org/pub/png/src/+
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+
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You may also want a copy of the PNG specification.  It is available+
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as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find+
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these at http://www.libpng.org/pub/png/pngdocs.html+
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+
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This code is currently being archived at libpng.sf.net in the+
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[DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)+
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at GO GRAPHSUP.  If you can't find it in any of those places,+
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e-mail me, and I'll help you find it.+
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+
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If you have any code changes, requests, problems, etc., please e-mail+
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them to me.  Also, I'd appreciate any make files or project files,+
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and any modifications you needed to make to get libpng to compile,+
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along with a #define variable to tell what compiler/system you are on.+
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If you needed to add transformations to libpng, or wish libpng would+
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provide the image in a different way, drop me a note (and code, if+
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possible), so I can consider supporting the transformation.+
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Finally, if you get any warning messages when compiling libpng+
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(note: not zlib), and they are easy to fix, I'd appreciate the+
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fix.  Please mention "libpng" somewhere in the subject line.  Thanks.+
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+
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This release was created and will be supported by myself (of course+
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based in a large way on Guy's and Andreas' earlier work), and the PNG group.+
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+
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Send comments/corrections/commendations to png-mng-implement at lists.sf.net+
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(subscription required; visit +
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https://lists.sourceforge.net/lists/listinfo/png-mng-implement+
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to subscribe) or to glennrp at users.sourceforge.net+
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+
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You can't reach Guy, the original libpng author, at the addresses+
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given in previous versions of this document.  He and Andreas will read mail+
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addressed to the png-mng-implement list, however.+
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+
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Please do not send general questions about PNG.  Send them to+
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the (png-mng-misc at lists.sourceforge.net, subscription required, visit+
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https://lists.sourceforge.net/lists/listinfo/png-mng-implement to subscribe)+
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On the other hand,+
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please do not send libpng questions to that address, send them to me+
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or to the png-mng-implement list.  I'll+
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get them in the end anyway.  If you have a question about something+
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in the PNG specification that is related to using libpng, send it+
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to me.  Send me any questions that start with "I was using libpng,+
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and ...".  If in doubt, send questions to me.  I'll bounce them+
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to others, if necessary.+
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+
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Please do not send suggestions on how to change PNG.  We have+
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been discussing PNG for twelve years now, and it is official and+
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finished.  If you have suggestions for libpng, however, I'll+
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gladly listen.  Even if your suggestion is not used immediately,+
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it may be used later.+
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+
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Files in this distribution:+
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+
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      ANNOUNCE      =>  Announcement of this version, with recent changes+
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      CHANGES       =>  Description of changes between libpng versions+
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      KNOWNBUG      =>  List of known bugs and deficiencies+
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      LICENSE       =>  License to use and redistribute libpng+
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      README        =>  This file+
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      TODO          =>  Things not implemented in the current library+
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      Y2KINFO       =>  Statement of Y2K compliance+
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      example.c     =>  Example code for using libpng functions+
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      libpng-*-*-diff.txt => Diff from previous release+
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      libpng.3      =>  manual page for libpng (includes libpng.txt)+
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      libpng.txt    =>  Description of libpng and its functions+
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      libpngpf.3    =>  manual page for libpng's private functions+
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      png.5         =>  manual page for the PNG format+
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      png.c         =>  Basic interface functions common to library+
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      png.h         =>  Library function and interface declarations+
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      pngconf.h     =>  System specific library configuration+
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      pngerror.c    =>  Error/warning message I/O functions+
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      pngget.c      =>  Functions for retrieving info from struct+
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      pngmem.c      =>  Memory handling functions+
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      pngbar.png    =>  PNG logo, 88x31+
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      pngnow.png    =>  PNG logo, 98x31+
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      pngpread.c    =>  Progressive reading functions+
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      pngread.c     =>  Read data/helper high-level functions+
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      pngrio.c      =>  Lowest-level data read I/O functions+
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      pngrtran.c    =>  Read data transformation functions+
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      pngrutil.c    =>  Read data utility functions+
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      pngset.c      =>  Functions for storing data into the info_struct+
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      pngtest.c     =>  Library test program+
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      pngtest.png   =>  Library test sample image+
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      pngtrans.c    =>  Common data transformation functions+
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      pngwio.c      =>  Lowest-level write I/O functions+
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      pngwrite.c    =>  High-level write functions+
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      pngwtran.c    =>  Write data transformations+
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      pngwutil.c    =>  Write utility functions+
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      contrib       =>  Contributions+
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       gregbook         =>  source code for PNG reading and writing, from+
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                            Greg Roelofs' "PNG: The Definitive Guide",+
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                            O'Reilly, 1999+
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       msvctest     =>  Builds and runs pngtest using a MSVC workspace+
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       pngminus     =>  Simple pnm2png and png2pnm programs+
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       pngsuite     =>  Test images+
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       visupng      =>  Contains a MSVC workspace for VisualPng+
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      projects      =>  Contains project files and workspaces for building DLL+
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       beos             =>  Contains a Beos workspace for building libpng+
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       c5builder        =>  Contains a Borland workspace for building libpng+
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                            and zlib+
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       visualc6         =>  Contains a Microsoft Visual C++ (MSVC) workspace+
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                            for building libpng and zlib+
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       netware.txt      =>  Contains instructions for downloading a set of+
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                            project files for building libpng and zlib on+
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                            Netware.+
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       wince.txt        =>  Contains instructions for downloading a Microsoft+
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                            Visual C++ (Windows CD Toolkit) workspace for+
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                            building libpng and zlib on WindowsCE+
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      scripts       =>  Directory containing scripts for building libpng:+
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       descrip.mms      =>  VMS makefile for MMS or MMK+
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       makefile.std     =>  Generic UNIX makefile (cc, creates static libpng.a)+
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       makefile.elf     =>  Linux/ELF makefile symbol versioning,+
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                            gcc, creates libpng12.so.0.1.2.40)+
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       makefile.linux   =>  Linux/ELF makefile+
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                            (gcc, creates libpng12.so.0.1.2.40)+
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       makefile.gcmmx   =>  Linux/ELF makefile+
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                            (gcc, creates libpng12.so.0.1.2.40,+
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                            uses assembler code tuned for Intel MMX platform)+
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       makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)+
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       makefile.knr     =>  Archaic UNIX Makefile that converts files with+
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                            ansi2knr (Requires ansi2knr.c from+
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                            ftp://ftp.cs.wisc.edu/ghost)+
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       makefile.aix     =>  AIX makefile+
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       makefile.cygwin  =>  Cygwin/gcc makefile+
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       makefile.darwin  =>  Darwin makefile+
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       makefile.dec     =>  DEC Alpha UNIX makefile+
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       makefile.freebsd =>  FreeBSD makefile+
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       makefile.hpgcc   =>  HPUX makefile using gcc+
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       makefile.hpux    =>  HPUX (10.20 and 11.00) makefile+
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       makefile.hp64    =>  HPUX (10.20 and 11.00) makefile, 64 bit+
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       makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)+
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       makefile.intel   =>  Intel C/C++ version 4.0 and later+
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       libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later+
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       makefile.netbsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng.so.+
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       makefile.ne12bsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng12.so+
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       makefile.openbsd =>  OpenBSD makefile+
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       makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)+
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       makefile.sggcc   =>  Silicon Graphics+
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                            (gcc, creates libpng12.so.0.1.2.40)+
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       makefile.sunos   =>  Sun makefile+
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       makefile.solaris =>  Solaris 2.X makefile+
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                            (gcc, creates libpng12.so.0.1.2.40)+
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       makefile.so9     =>  Solaris 9 makefile+
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                            (gcc, creates libpng12.so.0.1.2.40)+
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       makefile.32sunu  =>  Sun Ultra 32-bit makefile+
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       makefile.64sunu  =>  Sun Ultra 64-bit makefile+
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       makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc+
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       makefile.mips    =>  MIPS makefile+
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       makefile.acorn   =>  Acorn makefile+
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       makefile.amiga   =>  Amiga makefile+
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       smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC+
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                            compiler (Requires SCOPTIONS, copied from+
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                            scripts/SCOPTIONS.ppc)+
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       makefile.atari   =>  Atari makefile+
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       makefile.beos    =>  BEOS makefile for X86+
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       makefile.bor     =>  Borland makefile (uses bcc)+
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       makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)+
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       makefile.tc3     =>  Turbo C 3.0 makefile+
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       makefile.dj2     =>  DJGPP 2 makefile+
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       makefile.msc     =>  Microsoft C makefile+
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       makefile.vcawin32=>  makefile for Microsoft Visual C++ 5.0 and+
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                            later (uses assembler code tuned for Intel MMX+
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                            platform)+
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       makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and+
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                            later (does not use assembler code)+
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       makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)+
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       pngos2.def       =>  OS/2 module definition file used by makefile.os2+
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       makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model+
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       makevms.com      =>  VMS build script+
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       SCOPTIONS.ppc    =>  Used with smakefile.ppc+
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+
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Good luck, and happy coding.+
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+
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-Glenn Randers-Pehrson (current maintainer)+
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 Internet: glennrp at users.sourceforge.net+
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+
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-Andreas Eric Dilger (former maintainer, 1996-1997)+
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 Internet: adilger at enel.ucalgary.ca+
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 Web: http://members.shaw.ca/adilger/+
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+
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-Guy Eric Schalnat (original author and former maintainer, 1995-1996)+
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 (formerly of Group 42, Inc)+
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 Internet: gschal at infinet.com+
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