src/png/README

   1 README for libpng version 1.2.7 - September 12, 2004 (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 or libpng-*.tar.bz2 if you want UNIX-style line endings in the text
   8 files, or lpng*.zip if you want DOS-style line endings.
   9
  10 Version 0.89 was the first official release of libpng.  Don't let the
  11 fact that it's the first release fool you.  The libpng library has been in
  12 extensive use and testing since mid-1995.  By late 1997 it had
  13 finally gotten to the stage where there hadn't been significant
  14 changes to the API in some time, and people have a bad feeling about
  15 libraries with versions < 1.0.  Version 1.0.0 was released in
  16 March 1998.
  17
  18 ****
  19 Note that some of the changes to the png_info structure render this
  20 version of the library binary incompatible with libpng-0.89 or
  21 earlier versions if you are using a shared library.  The type of the
  22 "filler" parameter for png_set_filler() has changed from png_byte to
  23 png_uint_32, which will affect shared-library applications that use
  24 this function.
  25
  26 To avoid problems with changes to the internals of png_info_struct,
  27 new APIs have been made available in 0.95 to avoid direct application
  28 access to info_ptr.  These functions are the png_set_<chunk> and
  29 png_get_<chunk> functions.  These functions should be used when
  30 accessing/storing the info_struct data, rather than manipulating it
  31 directly, to avoid such problems in the future.
  32
  33 It is important to note that the APIs do not make current programs
  34 that access the info struct directly incompatible with the new
  35 library.  However, it is strongly suggested that new programs use
  36 the new APIs (as shown in example.c and pngtest.c), and older programs
  37 be converted to the new format, to facilitate upgrades in the future.
  38 ****
  39
  40 Additions since 0.90 include the ability to compile libpng as a
  41 Windows DLL, and new APIs for accessing data in the info struct.
  42 Experimental functions include the ability to set weighting and cost
  43 factors for row filter selection, direct reads of integers from buffers
  44 on big-endian processors that support misaligned data access, faster
  45 methods of doing alpha composition, and more accurate 16->8 bit color
  46 conversion.
  47
  48 The additions since 0.89 include the ability to read from a PNG stream
  49 which has had some (or all) of the signature bytes read by the calling
  50 application.  This also allows the reading of embedded PNG streams that
  51 do not have the PNG file signature.  As well, it is now possible to set
  52 the library action on the detection of chunk CRC errors.  It is possible
  53 to set different actions based on whether the CRC error occurred in a
  54 critical or an ancillary chunk.
  55
  56 The changes made to the library, and bugs fixed are based on discussions
  57 on the PNG-implement mailing list
  58 and not on material submitted privately to Guy, Andreas, or Glenn.  They will
  59 forward any good suggestions to the list.
  60
  61 For a detailed description on using libpng, read libpng.txt.  For
  62 examples of libpng in a program, see example.c and pngtest.c.  For usage
  63 information and restrictions (what little they are) on libpng, see
  64 png.h.  For a description on using zlib (the compression library used by
  65 libpng) and zlib's restrictions, see zlib.h
  66
  67 I have included a general makefile, as well as several machine and
  68 compiler specific ones, but you may have to modify one for your own needs.
  69
  70 You should use zlib 1.0.4 or later to run this, but it MAY work with
  71 versions as old as zlib 0.95.  Even so, there are bugs in older zlib
  72 versions which can cause the output of invalid compression streams for
  73 some images.  You will definitely need zlib 1.0.4 or later if you are
  74 taking advantage of the MS-DOS "far" structure allocation for the small
  75 and medium memory models.  You should also note that zlib is a
  76 compression library that is useful for more things than just PNG files.
  77 You can use zlib as a drop-in replacement for fread() and fwrite() if
  78 you are so inclined.
  79
  80 zlib should be available at the same place that libpng is, or at.
  81 ftp://ftp.info-zip.org/pub/infozip/zlib
  82
  83 You may also want a copy of the PNG specification.  It is available
  84 as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find
  85 these at http://www.libpng.org/pub/png/documents/
  86
  87 This code is currently being archived at libpng.sf.net in the
  88 [DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
  89 at GO GRAPHSUP.  If you can't find it in any of those places,
  90 e-mail me, and I'll help you find it.
  91
  92 If you have any code changes, requests, problems, etc., please e-mail
  93 them to me.  Also, I'd appreciate any make files or project files,
  94 and any modifications you needed to make to get libpng to compile,
  95 along with a #define variable to tell what compiler/system you are on.
  96 If you needed to add transformations to libpng, or wish libpng would
  97 provide the image in a different way, drop me a note (and code, if
  98 possible), so I can consider supporting the transformation.
  99 Finally, if you get any warning messages when compiling libpng
 100 (note: not zlib), and they are easy to fix, I'd appreciate the
 101 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
 102
 103 This release was created and will be supported by myself (of course
 104 based in a large way on Guy's and Andreas' earlier work), and the PNG group.
 105
 106 glennrp@users.sourceforge.net
 107 png-implement@ccrc.wustl.edu (subscription required; write to
 108 majordomo@ccrc.wustl.edu with "subscribe png-implement" in the message).
 109
 110 You can't reach Guy, the original libpng author, at the addresses
 111 given in previous versions of this document.  He and Andreas will read mail
 112 addressed to the png-implement list, however.
 113
 114 Please do not send general questions about PNG.  Send them to
 115 the (png-list@ccrc.wustl.edu, subscription required, write to
 116 majordomo@ccrc.wustl.edu with "subscribe png-list" in your message).
 117 On the other hand,
 118 please do not send libpng questions to that address, send them to me
 119 or to the png-implement list.  I'll
 120 get them in the end anyway.  If you have a question about something
 121 in the PNG specification that is related to using libpng, send it
 122 to me.  Send me any questions that start with "I was using libpng,
 123 and ...".  If in doubt, send questions to me.  I'll bounce them
 124 to others, if necessary.
 125
 126 Please do not send suggestions on how to change PNG.  We have
 127 been discussing PNG for nine years now, and it is official and
 128 finished.  If you have suggestions for libpng, however, I'll
 129 gladly listen.  Even if your suggestion is not used immediately,
 130 it may be used later.
 131
 132 Files in this distribution:
 133
 134       ANNOUNCE      =>  Announcement of this version, with recent changes
 135       CHANGES       =>  Description of changes between libpng versions
 136       KNOWNBUG      =>  List of known bugs and deficiencies
 137       LICENSE       =>  License to use and redistribute libpng
 138       README        =>  This file
 139       TODO          =>  Things not implemented in the current library
 140       Y2KINFO       =>  Statement of Y2K compliance
 141       example.c     =>  Example code for using libpng functions
 142       libpng.3      =>  manual page for libpng (includes libpng.txt)
 143       libpng.txt    =>  Description of libpng and its functions
 144       libpngpf.3    =>  manual page for libpng's private functions
 145       png.5         =>  manual page for the PNG format
 146       png.c         =>  Basic interface functions common to library
 147       png.h         =>  Library function and interface declarations
 148       pngconf.h     =>  System specific library configuration
 149       pngasmrd.h    =>  Header file for assembler-coded functions
 150       pngerror.c    =>  Error/warning message I/O functions
 151       pngget.c      =>  Functions for retrieving info from struct
 152       pngmem.c      =>  Memory handling functions
 153       pngbar.png    =>  PNG logo, 88x31
 154       pngnow.png    =>  PNG logo, 98x31
 155       pngpread.c    =>  Progressive reading functions
 156       pngread.c     =>  Read data/helper high-level functions
 157       pngrio.c      =>  Lowest-level data read I/O functions
 158       pngrtran.c    =>  Read data transformation functions
 159       pngrutil.c    =>  Read data utility functions
 160       pngset.c      =>  Functions for storing data into the info_struct
 161       pngtest.c     =>  Library test program
 162       pngtest.png   =>  Library test sample image
 163       pngtrans.c    =>  Common data transformation functions
 164       pngwio.c      =>  Lowest-level write I/O functions
 165       pngwrite.c    =>  High-level write functions
 166       pngwtran.c    =>  Write data transformations
 167       pngwutil.c    =>  Write utility functions
 168       contrib       =>  Contributions
 169        gregbook         =>  source code for PNG reading and writing, from
 170                             Greg Roelofs' "PNG: The Definitive Guide",
 171                             O'Reilly, 1999
 172        msvctest     =>  Builds and runs pngtest using a MSVC workspace
 173        pngminus     =>  Simple pnm2png and png2pnm programs
 174        pngsuite     =>  Test images
 175        visupng      =>  Contains a MSVC workspace for VisualPng
 176       projects      =>  Contains project files and workspaces for building DLL
 177        beos             =>  Contains a Beos workspace for building libpng
 178        c5builder        =>  Contains a Borland workspace for building libpng
 179                             and zlib
 180        visualc6         =>  Contains a Microsoft Visual C++ (MSVC) workspace
 181                             for building libpng and zlib
 182        netware.txt      =>  Contains instructions for downloading a set of
 183                             project files for building libpng and zlib on
 184                             Netware.
 185        wince.txt        =>  Contains instructions for downloading a Microsoft
 186                             Visual C++ (Windows CD Toolkit) workspace for
 187                             building libpng and zlib on WindowsCE
 188       scripts       =>  Directory containing scripts for building libpng:
 189        descrip.mms      =>  VMS makefile for MMS or MMK
 190        makefile.std     =>  Generic UNIX makefile (cc, creates static libpng.a)
 191        makefile.linux   =>  Linux/ELF makefile
 192                             (gcc, creates libpng12.so.0.1.2.7)
 193        makefile.gcmmx   =>  Linux/ELF makefile
 194                             (gcc, creates libpng12.so.0.1.2.7,
 195                             uses assembler code tuned for Intel MMX platform)
 196        makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)
 197        makefile.knr     =>  Archaic UNIX Makefile that converts files with
 198                             ansi2knr (Requires ansi2knr.c from
 199                             ftp://ftp.cs.wisc.edu/ghost)
 200        makefile.aix     =>  AIX makefile
 201        makefile.cygwin  =>  Cygwin/gcc makefile
 202        makefile.darwin  =>  Darwin makefile
 203        makefile.dec     =>  DEC Alpha UNIX makefile
 204        makefile.freebsd =>  FreeBSD makefile
 205        makefile.hpgcc   =>  HPUX makefile using gcc
 206        makefile.hpux    =>  HPUX (10.20 and 11.00) makefile
 207        makefile.hp64    =>  HPUX (10.20 and 11.00) makefile, 64 bit
 208        makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)
 209        makefile.intel   =>  Intel C/C++ version 4.0 and later
 210        libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later
 211        makefile.netbsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng.so.
 212        makefile.ne12bsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng12.so
 213        makefile.openbsd =>  OpenBSD makefile
 214        makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)
 215        makefile.sggcc   =>  Silicon Graphics
 216                             (gcc, creates libpng12.so.0.1.2.7)
 217        makefile.sunos   =>  Sun makefile
 218        makefile.solaris =>  Solaris 2.X makefile
 219                             (gcc, creates libpng12.so.0.1.2.7)
 220        makefile.so9     =>  Solaris 9 makefile
 221                             (gcc, creates libpng12.so.0.1.2.7)
 222        makefile.32sunu  =>  Sun Ultra 32-bit makefile
 223        makefile.64sunu  =>  Sun Ultra 64-bit makefile
 224        makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc
 225        makefile.mips    =>  MIPS makefile
 226        makefile.acorn   =>  Acorn makefile
 227        makefile.amiga   =>  Amiga makefile
 228        smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC
 229                             compiler (Requires SCOPTIONS, copied from
 230                             scripts/SCOPTIONS.ppc)
 231        makefile.atari   =>  Atari makefile
 232        makefile.beos    =>  BEOS makefile for X86
 233        makefile.bor     =>  Borland makefile (uses bcc)
 234        makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)
 235        makefile.tc3     =>  Turbo C 3.0 makefile
 236        makefile.dj2     =>  DJGPP 2 makefile
 237        makefile.msc     =>  Microsoft C makefile
 238        makefile.vcawin32=>  makefile for Microsoft Visual C++ 5.0 and
 239                             later (uses assembler code tuned for Intel MMX
 240                             platform)
 241        makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and
 242                             later (does not use assembler code)
 243        makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
 244        pngos2.def       =>  OS/2 module definition file used by makefile.os2
 245        makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model
 246        makevms.com      =>  VMS build script
 247        SCOPTIONS.ppc    =>  Used with smakefile.ppc
 248
 249 Good luck, and happy coding.
 250
 251 -Glenn Randers-Pehrson (current maintainer)
 252  Internet: glennrp@users.sourceforge.net
 253
 254 -Andreas Eric Dilger (former maintainer, 1996-1997)
 255  Internet: adilger@enel.ucalgary.ca
 256  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
 257
 258 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
 259  (formerly of Group 42, Inc)
 260  Internet: gschal@infinet.com