src/png/README

   1 README for libpng version 1.2.34 - December 18, 2008 (shared library 12.0)
   2 See the note about version numbers near the top of png.h
   3
   4 See INSTALL for instructions on how to install libpng.
   5
   6 Libpng comes in several distribution formats.  Get libpng-*.tar.gz,
   7 libpng-*.tar.lzma, or libpng-*.tar.bz2 if you want UNIX-style line
   8 endings in the text files, or lpng*.7z or lpng*.zip if you want DOS-style
   9 line endings.  You can get UNIX-style line endings from the *.zip file
  10 by using "unzip -a" but there seems to be no simple way to recover
  11 UNIX-style line endings from the *.7z file.  The *.tar.lzma file is
  12 recommended for *NIX users instead.
  13
  14 Version 0.89 was the first official release of libpng.  Don't let the
  15 fact that it's the first release fool you.  The libpng library has been in
  16 extensive use and testing since mid-1995.  By late 1997 it had
  17 finally gotten to the stage where there hadn't been significant
  18 changes to the API in some time, and people have a bad feeling about
  19 libraries with versions < 1.0.  Version 1.0.0 was released in
  20 March 1998.
  21
  22 ****
  23 Note that some of the changes to the png_info structure render this
  24 version of the library binary incompatible with libpng-0.89 or
  25 earlier versions if you are using a shared library.  The type of the
  26 "filler" parameter for png_set_filler() has changed from png_byte to
  27 png_uint_32, which will affect shared-library applications that use
  28 this function.
  29
  30 To avoid problems with changes to the internals of png_info_struct,
  31 new APIs have been made available in 0.95 to avoid direct application
  32 access to info_ptr.  These functions are the png_set_<chunk> and
  33 png_get_<chunk> functions.  These functions should be used when
  34 accessing/storing the info_struct data, rather than manipulating it
  35 directly, to avoid such problems in the future.
  36
  37 It is important to note that the APIs do not make current programs
  38 that access the info struct directly incompatible with the new
  39 library.  However, it is strongly suggested that new programs use
  40 the new APIs (as shown in example.c and pngtest.c), and older programs
  41 be converted to the new format, to facilitate upgrades in the future.
  42 ****
  43
  44 Additions since 0.90 include the ability to compile libpng as a
  45 Windows DLL, and new APIs for accessing data in the info struct.
  46 Experimental functions include the ability to set weighting and cost
  47 factors for row filter selection, direct reads of integers from buffers
  48 on big-endian processors that support misaligned data access, faster
  49 methods of doing alpha composition, and more accurate 16->8 bit color
  50 conversion.
  51
  52 The additions since 0.89 include the ability to read from a PNG stream
  53 which has had some (or all) of the signature bytes read by the calling
  54 application.  This also allows the reading of embedded PNG streams that
  55 do not have the PNG file signature.  As well, it is now possible to set
  56 the library action on the detection of chunk CRC errors.  It is possible
  57 to set different actions based on whether the CRC error occurred in a
  58 critical or an ancillary chunk.
  59
  60 The changes made to the library, and bugs fixed are based on discussions
  61 on the png-mng-implement mailing list
  62 and not on material submitted privately to Guy, Andreas, or Glenn.  They will
  63 forward any good suggestions to the list.
  64
  65 For a detailed description on using libpng, read libpng.txt.  For
  66 examples of libpng in a program, see example.c and pngtest.c.  For usage
  67 information and restrictions (what little they are) on libpng, see
  68 png.h.  For a description on using zlib (the compression library used by
  69 libpng) and zlib's restrictions, see zlib.h
  70
  71 I have included a general makefile, as well as several machine and
  72 compiler specific ones, but you may have to modify one for your own needs.
  73
  74 You should use zlib 1.0.4 or later to run this, but it MAY work with
  75 versions as old as zlib 0.95.  Even so, there are bugs in older zlib
  76 versions which can cause the output of invalid compression streams for
  77 some images.  You will definitely need zlib 1.0.4 or later if you are
  78 taking advantage of the MS-DOS "far" structure allocation for the small
  79 and medium memory models.  You should also note that zlib is a
  80 compression library that is useful for more things than just PNG files.
  81 You can use zlib as a drop-in replacement for fread() and fwrite() if
  82 you are so inclined.
  83
  84 zlib should be available at the same place that libpng is, or at
  85 ftp://ftp.simplesystems.org/pub/png/src/
  86
  87 You may also want a copy of the PNG specification.  It is available
  88 as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find
  89 these at http://www.libpng.org/pub/png/pngdocs.html
  90
  91 This code is currently being archived at libpng.sf.net in the
  92 [DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
  93 at GO GRAPHSUP.  If you can't find it in any of those places,
  94 e-mail me, and I'll help you find it.
  95
  96 If you have any code changes, requests, problems, etc., please e-mail
  97 them to me.  Also, I'd appreciate any make files or project files,
  98 and any modifications you needed to make to get libpng to compile,
  99 along with a #define variable to tell what compiler/system you are on.
 100 If you needed to add transformations to libpng, or wish libpng would
 101 provide the image in a different way, drop me a note (and code, if
 102 possible), so I can consider supporting the transformation.
 103 Finally, if you get any warning messages when compiling libpng
 104 (note: not zlib), and they are easy to fix, I'd appreciate the
 105 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
 106
 107 This release was created and will be supported by myself (of course
 108 based in a large way on Guy's and Andreas' earlier work), and the PNG group.
 109
 110 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 111 (subscription required; visit
 112 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
 113 to subscribe) or to glennrp at users.sourceforge.net
 114
 115 You can't reach Guy, the original libpng author, at the addresses
 116 given in previous versions of this document.  He and Andreas will read mail
 117 addressed to the png-mng-implement list, however.
 118
 119 Please do not send general questions about PNG.  Send them to
 120 the (png-mng-misc at lists.sourceforge.net, subscription required, visit
 121 https://lists.sourceforge.net/lists/listinfo/png-mng-implement to subscribe)
 122 On the other hand,
 123 please do not send libpng questions to that address, send them to me
 124 or to the png-mng-implement list.  I'll
 125 get them in the end anyway.  If you have a question about something
 126 in the PNG specification that is related to using libpng, send it
 127 to me.  Send me any questions that start with "I was using libpng,
 128 and ...".  If in doubt, send questions to me.  I'll bounce them
 129 to others, if necessary.
 130
 131 Please do not send suggestions on how to change PNG.  We have
 132 been discussing PNG for twelve years now, and it is official and
 133 finished.  If you have suggestions for libpng, however, I'll
 134 gladly listen.  Even if your suggestion is not used immediately,
 135 it may be used later.
 136
 137 Files in this distribution:
 138
 139       ANNOUNCE      =>  Announcement of this version, with recent changes
 140       CHANGES       =>  Description of changes between libpng versions
 141       KNOWNBUG      =>  List of known bugs and deficiencies
 142       LICENSE       =>  License to use and redistribute libpng
 143       README        =>  This file
 144       TODO          =>  Things not implemented in the current library
 145       Y2KINFO       =>  Statement of Y2K compliance
 146       example.c     =>  Example code for using libpng functions
 147       libpng-*-*-diff.txt => Diff from previous release
 148       libpng.3      =>  manual page for libpng (includes libpng.txt)
 149       libpng.txt    =>  Description of libpng and its functions
 150       libpngpf.3    =>  manual page for libpng's private functions
 151       png.5         =>  manual page for the PNG format
 152       png.c         =>  Basic interface functions common to library
 153       png.h         =>  Library function and interface declarations
 154       pngconf.h     =>  System specific library configuration
 155       pngerror.c    =>  Error/warning message I/O functions
 156       pngget.c      =>  Functions for retrieving info from struct
 157       pngmem.c      =>  Memory handling functions
 158       pngbar.png    =>  PNG logo, 88x31
 159       pngnow.png    =>  PNG logo, 98x31
 160       pngpread.c    =>  Progressive reading functions
 161       pngread.c     =>  Read data/helper high-level functions
 162       pngrio.c      =>  Lowest-level data read I/O functions
 163       pngrtran.c    =>  Read data transformation functions
 164       pngrutil.c    =>  Read data utility functions
 165       pngset.c      =>  Functions for storing data into the info_struct
 166       pngtest.c     =>  Library test program
 167       pngtest.png   =>  Library test sample image
 168       pngtrans.c    =>  Common data transformation functions
 169       pngwio.c      =>  Lowest-level write I/O functions
 170       pngwrite.c    =>  High-level write functions
 171       pngwtran.c    =>  Write data transformations
 172       pngwutil.c    =>  Write utility functions
 173       contrib       =>  Contributions
 174        gregbook         =>  source code for PNG reading and writing, from
 175                             Greg Roelofs' "PNG: The Definitive Guide",
 176                             O'Reilly, 1999
 177        msvctest     =>  Builds and runs pngtest using a MSVC workspace
 178        pngminus     =>  Simple pnm2png and png2pnm programs
 179        pngsuite     =>  Test images
 180        visupng      =>  Contains a MSVC workspace for VisualPng
 181       projects      =>  Contains project files and workspaces for building DLL
 182        beos             =>  Contains a Beos workspace for building libpng
 183        c5builder        =>  Contains a Borland workspace for building libpng
 184                             and zlib
 185        visualc6         =>  Contains a Microsoft Visual C++ (MSVC) workspace
 186                             for building libpng and zlib
 187        netware.txt      =>  Contains instructions for downloading a set of
 188                             project files for building libpng and zlib on
 189                             Netware.
 190        wince.txt        =>  Contains instructions for downloading a Microsoft
 191                             Visual C++ (Windows CD Toolkit) workspace for
 192                             building libpng and zlib on WindowsCE
 193       scripts       =>  Directory containing scripts for building libpng:
 194        descrip.mms      =>  VMS makefile for MMS or MMK
 195        makefile.std     =>  Generic UNIX makefile (cc, creates static libpng.a)
 196        makefile.elf     =>  Linux/ELF makefile symbol versioning,
 197                             gcc, creates libpng12.so.0.1.2.34)
 198        makefile.linux   =>  Linux/ELF makefile
 199                             (gcc, creates libpng12.so.0.1.2.34)
 200        makefile.gcmmx   =>  Linux/ELF makefile
 201                             (gcc, creates libpng12.so.0.1.2.34,
 202                             uses assembler code tuned for Intel MMX platform)
 203        makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)
 204        makefile.knr     =>  Archaic UNIX Makefile that converts files with
 205                             ansi2knr (Requires ansi2knr.c from
 206                             ftp://ftp.cs.wisc.edu/ghost)
 207        makefile.aix     =>  AIX makefile
 208        makefile.cygwin  =>  Cygwin/gcc makefile
 209        makefile.darwin  =>  Darwin makefile
 210        makefile.dec     =>  DEC Alpha UNIX makefile
 211        makefile.freebsd =>  FreeBSD makefile
 212        makefile.hpgcc   =>  HPUX makefile using gcc
 213        makefile.hpux    =>  HPUX (10.20 and 11.00) makefile
 214        makefile.hp64    =>  HPUX (10.20 and 11.00) makefile, 64 bit
 215        makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)
 216        makefile.intel   =>  Intel C/C++ version 4.0 and later
 217        libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later
 218        makefile.netbsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng.so.
 219        makefile.ne12bsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng12.so
 220        makefile.openbsd =>  OpenBSD makefile
 221        makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)
 222        makefile.sggcc   =>  Silicon Graphics
 223                             (gcc, creates libpng12.so.0.1.2.34)
 224        makefile.sunos   =>  Sun makefile
 225        makefile.solaris =>  Solaris 2.X makefile
 226                             (gcc, creates libpng12.so.0.1.2.34)
 227        makefile.so9     =>  Solaris 9 makefile
 228                             (gcc, creates libpng12.so.0.1.2.34)
 229        makefile.32sunu  =>  Sun Ultra 32-bit makefile
 230        makefile.64sunu  =>  Sun Ultra 64-bit makefile
 231        makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc
 232        makefile.mips    =>  MIPS makefile
 233        makefile.acorn   =>  Acorn makefile
 234        makefile.amiga   =>  Amiga makefile
 235        smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC
 236                             compiler (Requires SCOPTIONS, copied from
 237                             scripts/SCOPTIONS.ppc)
 238        makefile.atari   =>  Atari makefile
 239        makefile.beos    =>  BEOS makefile for X86
 240        makefile.bor     =>  Borland makefile (uses bcc)
 241        makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)
 242        makefile.tc3     =>  Turbo C 3.0 makefile
 243        makefile.dj2     =>  DJGPP 2 makefile
 244        makefile.msc     =>  Microsoft C makefile
 245        makefile.vcawin32=>  makefile for Microsoft Visual C++ 5.0 and
 246                             later (uses assembler code tuned for Intel MMX
 247                             platform)
 248        makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and
 249                             later (does not use assembler code)
 250        makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
 251        pngos2.def       =>  OS/2 module definition file used by makefile.os2
 252        makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model
 253        makevms.com      =>  VMS build script
 254        SCOPTIONS.ppc    =>  Used with smakefile.ppc
 255
 256 Good luck, and happy coding.
 257
 258 -Glenn Randers-Pehrson (current maintainer)
 259  Internet: glennrp at users.sourceforge.net
 260
 261 -Andreas Eric Dilger (former maintainer, 1996-1997)
 262  Internet: adilger at enel.ucalgary.ca
 263  Web: http://members.shaw.ca/adilger/
 264
 265 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
 266  (formerly of Group 42, Inc)
 267  Internet: gschal at infinet.com