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1.3 @@ -0,0 +1,202 @@
1.4 +README for libpng version 1.6.10 - March 6, 2014 (shared library 16.0)
1.5 +See the note about version numbers near the top of png.h
1.6 +
1.7 +See INSTALL for instructions on how to install libpng.
1.8 +
1.9 +Libpng comes in several distribution formats. Get libpng-*.tar.gz or
1.10 +libpng-*.tar.xz or if you want UNIX-style line endings in the text files,
1.11 +or lpng*.7z or lpng*.zip if you want DOS-style line endings.
1.12 +
1.13 +Version 0.89 was the first official release of libpng. Don't let the
1.14 +fact that it's the first release fool you. The libpng library has been in
1.15 +extensive use and testing since mid-1995. By late 1997 it had
1.16 +finally gotten to the stage where there hadn't been significant
1.17 +changes to the API in some time, and people have a bad feeling about
1.18 +libraries with versions < 1.0. Version 1.0.0 was released in
1.19 +March 1998.
1.20 +
1.21 +****
1.22 +Note that some of the changes to the png_info structure render this
1.23 +version of the library binary incompatible with libpng-0.89 or
1.24 +earlier versions if you are using a shared library. The type of the
1.25 +"filler" parameter for png_set_filler() has changed from png_byte to
1.26 +png_uint_32, which will affect shared-library applications that use
1.27 +this function.
1.28 +
1.29 +To avoid problems with changes to the internals of png_info_struct,
1.30 +new APIs have been made available in 0.95 to avoid direct application
1.31 +access to info_ptr. These functions are the png_set_<chunk> and
1.32 +png_get_<chunk> functions. These functions should be used when
1.33 +accessing/storing the info_struct data, rather than manipulating it
1.34 +directly, to avoid such problems in the future.
1.35 +
1.36 +It is important to note that the APIs do not make current programs
1.37 +that access the info struct directly incompatible with the new
1.38 +library. However, it is strongly suggested that new programs use
1.39 +the new APIs (as shown in example.c and pngtest.c), and older programs
1.40 +be converted to the new format, to facilitate upgrades in the future.
1.41 +****
1.42 +
1.43 +Additions since 0.90 include the ability to compile libpng as a
1.44 +Windows DLL, and new APIs for accessing data in the info struct.
1.45 +Experimental functions include the ability to set weighting and cost
1.46 +factors for row filter selection, direct reads of integers from buffers
1.47 +on big-endian processors that support misaligned data access, faster
1.48 +methods of doing alpha composition, and more accurate 16->8 bit color
1.49 +conversion.
1.50 +
1.51 +The additions since 0.89 include the ability to read from a PNG stream
1.52 +which has had some (or all) of the signature bytes read by the calling
1.53 +application. This also allows the reading of embedded PNG streams that
1.54 +do not have the PNG file signature. As well, it is now possible to set
1.55 +the library action on the detection of chunk CRC errors. It is possible
1.56 +to set different actions based on whether the CRC error occurred in a
1.57 +critical or an ancillary chunk.
1.58 +
1.59 +The changes made to the library, and bugs fixed are based on discussions
1.60 +on the PNG-implement mailing list and not on material submitted
1.61 +privately to Guy, Andreas, or Glenn. They will forward any good
1.62 +suggestions to the list.
1.63 +
1.64 +For a detailed description on using libpng, read libpng-manual.txt. For
1.65 +examples of libpng in a program, see example.c and pngtest.c. For usage
1.66 +information and restrictions (what little they are) on libpng, see
1.67 +png.h. For a description on using zlib (the compression library used by
1.68 +libpng) and zlib's restrictions, see zlib.h
1.69 +
1.70 +I have included a general makefile, as well as several machine and
1.71 +compiler specific ones, but you may have to modify one for your own needs.
1.72 +
1.73 +You should use zlib 1.0.4 or later to run this, but it MAY work with
1.74 +versions as old as zlib 0.95. Even so, there are bugs in older zlib
1.75 +versions which can cause the output of invalid compression streams for
1.76 +some images. You will definitely need zlib 1.0.4 or later if you are
1.77 +taking advantage of the MS-DOS "far" structure allocation for the small
1.78 +and medium memory models. You should also note that zlib is a
1.79 +compression library that is useful for more things than just PNG files.
1.80 +You can use zlib as a drop-in replacement for fread() and fwrite() if
1.81 +you are so inclined.
1.82 +
1.83 +zlib should be available at the same place that libpng is, or at zlib.net.
1.84 +
1.85 +You may also want a copy of the PNG specification. It is available
1.86 +as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
1.87 +these at http://www.libpng.org/pub/png/documents/
1.88 +
1.89 +This code is currently being archived at libpng.sf.net in the
1.90 +[DOWNLOAD] area, and at ftp://ftp.simplesystems.org. If you can't find it
1.91 +in any of those places, e-mail me, and I'll help you find it.
1.92 +
1.93 +If you have any code changes, requests, problems, etc., please e-mail
1.94 +them to me. Also, I'd appreciate any make files or project files,
1.95 +and any modifications you needed to make to get libpng to compile,
1.96 +along with a #define variable to tell what compiler/system you are on.
1.97 +If you needed to add transformations to libpng, or wish libpng would
1.98 +provide the image in a different way, drop me a note (and code, if
1.99 +possible), so I can consider supporting the transformation.
1.100 +Finally, if you get any warning messages when compiling libpng
1.101 +(note: not zlib), and they are easy to fix, I'd appreciate the
1.102 +fix. Please mention "libpng" somewhere in the subject line. Thanks.
1.103 +
1.104 +This release was created and will be supported by myself (of course
1.105 +based in a large way on Guy's and Andreas' earlier work), and the PNG
1.106 +development group.
1.107 +
1.108 +Send comments/corrections/commendations to png-mng-implement at
1.109 +lists.sourceforge.net (subscription required; visit
1.110 +https://lists.sourceforge.net/lists/listinfo/png-mng-implement
1.111 +to subscribe) or to glennrp at users.sourceforge.net
1.112 +
1.113 +You can't reach Guy, the original libpng author, at the addresses
1.114 +given in previous versions of this document. He and Andreas will
1.115 +read mail addressed to the png-implement list, however.
1.116 +
1.117 +Please do not send general questions about PNG. Send them to
1.118 +png-mng-misc at lists.sf.net (subscription required; visit
1.119 +https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
1.120 +subscribe). If you have a question about something
1.121 +in the PNG specification that is related to using libpng, send it
1.122 +to me. Send me any questions that start with "I was using libpng,
1.123 +and ...". If in doubt, send questions to me. I'll bounce them
1.124 +to others, if necessary.
1.125 +
1.126 +Please do not send suggestions on how to change PNG. We have
1.127 +been discussing PNG for nineteen years now, and it is official and
1.128 +finished. If you have suggestions for libpng, however, I'll
1.129 +gladly listen. Even if your suggestion is not used immediately,
1.130 +it may be used later.
1.131 +
1.132 +Files in this distribution:
1.133 +
1.134 + ANNOUNCE => Announcement of this version, with recent changes
1.135 + CHANGES => Description of changes between libpng versions
1.136 + KNOWNBUG => List of known bugs and deficiencies
1.137 + LICENSE => License to use and redistribute libpng
1.138 + README => This file
1.139 + TODO => Things not implemented in the current library
1.140 + Y2KINFO => Statement of Y2K compliance
1.141 + example.c => Example code for using libpng functions
1.142 + libpng.3 => manual page for libpng (includes libpng-manual.txt)
1.143 + libpng-manual.txt => Description of libpng and its functions
1.144 + libpngpf.3 => manual page for libpng's private functions
1.145 + png.5 => manual page for the PNG format
1.146 + png.c => Basic interface functions common to library
1.147 + png.h => Library function and interface declarations (public)
1.148 + pngpriv.h => Library function and interface declarations (private)
1.149 + pngconf.h => System specific library configuration (public)
1.150 + pngstruct.h => png_struct declaration (private)
1.151 + pnginfo.h => png_info struct declaration (private)
1.152 + pngdebug.h => debugging macros (private)
1.153 + pngerror.c => Error/warning message I/O functions
1.154 + pngget.c => Functions for retrieving info from struct
1.155 + pngmem.c => Memory handling functions
1.156 + pngbar.png => PNG logo, 88x31
1.157 + pngnow.png => PNG logo, 98x31
1.158 + pngpread.c => Progressive reading functions
1.159 + pngread.c => Read data/helper high-level functions
1.160 + pngrio.c => Lowest-level data read I/O functions
1.161 + pngrtran.c => Read data transformation functions
1.162 + pngrutil.c => Read data utility functions
1.163 + pngset.c => Functions for storing data into the info_struct
1.164 + pngtest.c => Library test program
1.165 + pngtest.png => Library test sample image
1.166 + pngtrans.c => Common data transformation functions
1.167 + pngwio.c => Lowest-level write I/O functions
1.168 + pngwrite.c => High-level write functions
1.169 + pngwtran.c => Write data transformations
1.170 + pngwutil.c => Write utility functions
1.171 + arm => Contains optimized code for the ARM platform
1.172 + contrib => Contributions
1.173 + examples => Example programs
1.174 + gregbook => source code for PNG reading and writing, from
1.175 + Greg Roelofs' "PNG: The Definitive Guide",
1.176 + O'Reilly, 1999
1.177 + libtests => Test programs
1.178 + pngminim => Minimal decoder, encoder, and progressive decoder
1.179 + programs demonstrating use of pngusr.dfa
1.180 + pngminus => Simple pnm2png and png2pnm programs
1.181 + pngsuite => Test images
1.182 + tools => Various tools
1.183 + visupng => Contains a MSVC workspace for VisualPng
1.184 + projects => Contains project files and workspaces for
1.185 + building a DLL
1.186 + owatcom => Contains a WATCOM project for building libpng
1.187 + visualc71 => Contains a Microsoft Visual C++ (MSVC)
1.188 + workspace for building libpng and zlib
1.189 + vstudio => Contains a Microsoft Visual C++ (MSVC)
1.190 + workspace for building libpng and zlib
1.191 + scripts => Directory containing scripts for building libpng:
1.192 + (see scripts/README.txt for the list of scripts)
1.193 +
1.194 +Good luck, and happy coding.
1.195 +
1.196 +-Glenn Randers-Pehrson (current maintainer, since 1998)
1.197 + Internet: glennrp at users.sourceforge.net
1.198 +
1.199 +-Andreas Eric Dilger (former maintainer, 1996-1997)
1.200 + Internet: adilger at enel.ucalgary.ca
1.201 + Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
1.202 +
1.203 +-Guy Eric Schalnat (original author and former maintainer, 1995-1996)
1.204 + (formerly of Group 42, Inc)
1.205 + Internet: gschal at infinet.com
