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README for libpng version 1.2.7 - September 12, 2004 (shared library 12.0)
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See the note about version numbers near the top of png.h
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See INSTALL for instructions on how to install libpng.
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Libpng comes in several distribution formats. Get libpng-*.tar.gz
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or libpng-*.tar.bz2 if you want UNIX-style line endings in the text
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files, or lpng*.zip if you want DOS-style line endings.
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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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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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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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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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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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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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The changes made to the library, and bugs fixed are based on discussions
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on the PNG-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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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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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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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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zlib should be available at the same place that libpng is, or at.
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ftp://ftp.info-zip.org/pub/infozip/zlib
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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/documents/
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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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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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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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glennrp@users.sourceforge.net
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png-implement@ccrc.wustl.edu (subscription required; write to
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majordomo@ccrc.wustl.edu with "subscribe png-implement" in the message).
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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-implement list, however.
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Please do not send general questions about PNG. Send them to
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the (png-list@ccrc.wustl.edu, subscription required, write to
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majordomo@ccrc.wustl.edu with "subscribe png-list" in your message).
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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-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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Please do not send suggestions on how to change PNG. We have
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been discussing PNG for nine 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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Files in this distribution:
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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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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.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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pngasmrd.h => Header file for assembler-coded functions
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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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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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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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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.linux => Linux/ELF makefile
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(gcc, creates libpng12.so.0.1.2.7)
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makefile.gcmmx => Linux/ELF makefile
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(gcc, creates libpng12.so.0.1.2.7,
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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.0.1.2.7)
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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.0.1.2.7)
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makefile.so9 => Solaris 9 makefile
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(gcc, creates libpng12.so.0.1.2.7)
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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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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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Good luck, and happy coding.
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-Glenn Randers-Pehrson (current maintainer)
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Internet: glennrp@users.sourceforge.net
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-Andreas Eric Dilger (former maintainer, 1996-1997)
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Internet: adilger@enel.ucalgary.ca
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Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
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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@infinet.com
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png/README
