4418N/AREADME for libpng version 1.5.4 - July 7, 2011 (shared library 15.0)
0N/ASee the note about version numbers near the top of
png.h 0N/ASee INSTALL for instructions on how to install libpng.
4418N/ALibpng comes in several distribution formats. Get libpng-*
.tar.gz,
4418N/Ain the text files, or lpng*.zip if you want DOS-style line endings.
0N/AVersion 0.89 was the first official release of libpng. Don't let the
0N/Afact that it's the first release fool you. The libpng library has been in
0N/Aextensive use and testing since mid-1995. By late 1997 it had
0N/Afinally gotten to the stage where there hadn't been significant
0N/Achanges to the API in some time, and people have a bad feeling about
0N/Alibraries with versions < 1.0. Version 1.0.0 was released in
0N/ANote that some of the changes to the png_info structure render this
0N/Aversion of the library binary incompatible with libpng-0.89 or
0N/Aearlier versions if you are using a shared library. The type of the
0N/A"filler" parameter for png_set_filler() has changed from png_byte to
0N/Apng_uint_32, which will affect shared-library applications that use
0N/ATo avoid problems with changes to the internals of png_info_struct,
0N/Anew APIs have been made available in 0.95 to avoid direct application
0N/Aaccess to info_ptr. These functions are the png_set_<chunk> and
0N/Apng_get_<chunk> functions. These functions should be used when
0N/Adirectly, to avoid such problems in the future.
0N/AIt is important to note that the APIs do not make current programs
0N/Athat access the info struct directly incompatible with the new
0N/Alibrary. However, it is strongly suggested that new programs use
0N/Abe converted to the new format, to facilitate upgrades in the future.
0N/AAdditions since 0.90 include the ability to compile libpng as a
0N/AWindows DLL, and new APIs for accessing data in the info struct.
0N/AExperimental functions include the ability to set weighting and cost
0N/Afactors for row filter selection, direct reads of integers from buffers
0N/Aon big-endian processors that support misaligned data access, faster
0N/Amethods of doing alpha composition, and more accurate 16->8 bit color
0N/AThe additions since 0.89 include the ability to read from a PNG stream
0N/Awhich has had some (or all) of the signature bytes read by the calling
0N/Aapplication. This also allows the reading of embedded PNG streams that
0N/Ado not have the PNG file signature. As well, it is now possible to set
0N/Athe library action on the detection of chunk CRC errors. It is possible
0N/Ato set different actions based on whether the CRC error occurred in a
0N/Acritical or an ancillary chunk.
0N/AThe changes made to the library, and bugs fixed are based on discussions
4418N/Aon the PNG-implement mailing list and not on material submitted
4418N/Aprivately to Guy, Andreas, or Glenn. They will forward any good
0N/Ainformation and restrictions (what little they are) on libpng, see
0N/Apng.h. For a description on using zlib (the compression library used by
0N/AI have included a general makefile, as well as several machine and
0N/Acompiler specific ones, but you may have to modify one for your own needs.
0N/AYou should use zlib 1.0.4 or later to run this, but it MAY work with
0N/Aversions as old as zlib 0.95. Even so, there are bugs in older zlib
0N/Aversions which can cause the output of invalid compression streams for
0N/Asome images. You will definitely need zlib 1.0.4 or later if you are
0N/Ataking advantage of the MS-DOS "far" structure allocation for the small
0N/Aand medium memory models. You should also note that zlib is a
0N/Acompression library that is useful for more things than just PNG files.
0N/AYou can use zlib as a drop-in replacement for fread() and fwrite() if
0N/Azlib should be available at the same place that libpng is, or at.
0N/AYou may also want a copy of the PNG specification. It is available
0N/Aas an RFC, a W3C Recommendation, and an
ISO/IEC Standard. You can find
0N/A[DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
0N/Aat GO GRAPHSUP. If you can't find it in any of those places,
0N/Ae-mail me, and I'll help you find it.
0N/AIf you have any code changes, requests, problems, etc., please e-mail
0N/Athem to me. Also, I'd appreciate any make files or project files,
0N/Aand any modifications you needed to make to get libpng to compile,
0N/AIf you needed to add transformations to libpng, or wish libpng would
0N/Aprovide the image in a different way, drop me a note (and code, if
0N/Apossible), so I can consider supporting the transformation.
0N/AFinally, if you get any warning messages when compiling libpng
0N/A(note: not zlib), and they are easy to fix, I'd appreciate the
0N/Afix. Please mention "libpng" somewhere in the subject line. Thanks.
0N/AThis release was created and will be supported by myself (of course
4418N/Abased in a large way on Guy's and Andreas' earlier work), and the PNG
0N/AYou can't reach Guy, the original libpng author, at the addresses
4418N/Agiven in previous versions of this document. He and Andreas will
4418N/Aread mail addressed to the png-implement list, however.
0N/APlease do not send general questions about PNG. Send them to
4418N/Asubscribe). If you have a question about something
0N/Ain the PNG specification that is related to using libpng, send it
0N/Ato me. Send me any questions that start with "I was using libpng,
0N/Aand ...". If in doubt, send questions to me. I'll bounce them
0N/Ato others, if necessary.
0N/APlease do not send suggestions on how to change PNG. We have
4418N/Abeen discussing PNG for sixteen years now, and it is official and
0N/Afinished. If you have suggestions for libpng, however, I'll
0N/Agladly listen. Even if your suggestion is not used immediately,
0N/Ait may be used later.
0N/AFiles in this distribution:
0N/A ANNOUNCE => Announcement of this version, with recent changes
0N/A CHANGES => Description of changes between libpng versions
0N/A KNOWNBUG => List of known bugs and deficiencies
0N/A LICENSE => License to use and redistribute libpng
0N/A TODO => Things not implemented in the current library
0N/A Y2KINFO => Statement of Y2K compliance
0N/A libpngpf.3 => manual page for libpng's private functions
0N/A png.5 => manual page for the PNG format
0N/A png.c => Basic interface functions common to library
4418N/A png.h => Library function and interface declarations (public)
0N/A pngset.c => Functions for storing data into the info_struct
0N/A contrib => Contributions
0N/A gregbook => source code for PNG reading and writing, from
0N/A Greg Roelofs' "PNG: The Definitive Guide",
0N/A msvctest => Builds and runs pngtest using a MSVC workspace
0N/A pngminus => Simple pnm2png and png2pnm programs
0N/A pngsuite => Test images
0N/A visupng => Contains a MSVC workspace for VisualPng
4418N/A projects => Contains project files and workspaces for
4418N/A cbuilder5 => Contains a Borland workspace for building
4418N/A visualc6 => Contains a Microsoft Visual C++ (MSVC)
4418N/A workspace for building libpng and zlib
4418N/A visualc71 => Contains a Microsoft Visual C++ (MSVC)
4418N/A workspace for building libpng and zlib
4418N/A xcode => Contains an Apple xcode
4418N/A workspace for building libpng and zlib
0N/A scripts => Directory containing scripts for building libpng:
0N/AGood luck, and happy coding.
4418N/A-Glenn Randers-Pehrson (current maintainer, since 1998)
0N/A-Andreas Eric Dilger (former maintainer, 1996-1997)
0N/A-Guy Eric Schalnat (original author and former maintainer, 1995-1996)
0N/A (formerly of Group 42, Inc)
