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    1 README for libpng version 1.2.12 - June 27, 2006 (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 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
  107 (subscription required; visit 
  108 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
  109 to subscribe) or to glennrp at users.sourceforge.net
  110 
  111 You can't reach Guy, the original libpng author, at the addresses
  112 given in previous versions of this document.  He and Andreas will read mail
  113 addressed to the png-implement list, however.
  114 
  115 Please do not send general questions about PNG.  Send them to
  116 the (png-list at ccrc.wustl.edu, subscription required, write to
  117 majordomo at ccrc.wustl.edu with "subscribe png-list" in your message).
  118 On the other hand,
  119 please do not send libpng questions to that address, send them to me
  120 or to the png-implement list.  I'll
  121 get them in the end anyway.  If you have a question about something
  122 in the PNG specification that is related to using libpng, send it
  123 to me.  Send me any questions that start with "I was using libpng,
  124 and ...".  If in doubt, send questions to me.  I'll bounce them
  125 to others, if necessary.
  126 
  127 Please do not send suggestions on how to change PNG.  We have
  128 been discussing PNG for nine years now, and it is official and
  129 finished.  If you have suggestions for libpng, however, I'll
  130 gladly listen.  Even if your suggestion is not used immediately,
  131 it may be used later.
  132 
  133 Files in this distribution:
  134 
  135       ANNOUNCE      =>  Announcement of this version, with recent changes
  136       CHANGES       =>  Description of changes between libpng versions
  137       KNOWNBUG      =>  List of known bugs and deficiencies
  138       LICENSE       =>  License to use and redistribute libpng
  139       README        =>  This file
  140       TODO          =>  Things not implemented in the current library
  141       Y2KINFO       =>  Statement of Y2K compliance
  142       example.c     =>  Example code for using libpng functions
  143       libpng.3      =>  manual page for libpng (includes libpng.txt)
  144       libpng.txt    =>  Description of libpng and its functions
  145       libpngpf.3    =>  manual page for libpng's private functions
  146       png.5         =>  manual page for the PNG format
  147       png.c         =>  Basic interface functions common to library
  148       png.h         =>  Library function and interface declarations
  149       pngconf.h     =>  System specific library configuration
  150       pngasmrd.h    =>  Header file for assembler-coded functions
  151       pngerror.c    =>  Error/warning message I/O functions
  152       pngget.c      =>  Functions for retrieving info from struct
  153       pngmem.c      =>  Memory handling functions
  154       pngbar.png    =>  PNG logo, 88x31
  155       pngnow.png    =>  PNG logo, 98x31
  156       pngpread.c    =>  Progressive reading functions
  157       pngread.c     =>  Read data/helper high-level functions
  158       pngrio.c      =>  Lowest-level data read I/O functions
  159       pngrtran.c    =>  Read data transformation functions
  160       pngrutil.c    =>  Read data utility functions
  161       pngset.c      =>  Functions for storing data into the info_struct
  162       pngtest.c     =>  Library test program
  163       pngtest.png   =>  Library test sample image
  164       pngtrans.c    =>  Common data transformation functions
  165       pngwio.c      =>  Lowest-level write I/O functions
  166       pngwrite.c    =>  High-level write functions
  167       pngwtran.c    =>  Write data transformations
  168       pngwutil.c    =>  Write utility functions
  169       contrib       =>  Contributions
  170        gregbook         =>  source code for PNG reading and writing, from
  171                             Greg Roelofs' "PNG: The Definitive Guide",
  172                             O'Reilly, 1999
  173        msvctest     =>  Builds and runs pngtest using a MSVC workspace
  174        pngminus     =>  Simple pnm2png and png2pnm programs
  175        pngsuite     =>  Test images
  176        visupng      =>  Contains a MSVC workspace for VisualPng
  177       projects      =>  Contains project files and workspaces for building DLL
  178        beos             =>  Contains a Beos workspace for building libpng
  179        c5builder        =>  Contains a Borland workspace for building libpng
  180                             and zlib
  181        visualc6         =>  Contains a Microsoft Visual C++ (MSVC) workspace
  182                             for building libpng and zlib
  183        netware.txt      =>  Contains instructions for downloading a set of
  184                             project files for building libpng and zlib on
  185                             Netware.
  186        wince.txt        =>  Contains instructions for downloading a Microsoft
  187                             Visual C++ (Windows CD Toolkit) workspace for
  188                             building libpng and zlib on WindowsCE
  189       scripts       =>  Directory containing scripts for building libpng:
  190        descrip.mms      =>  VMS makefile for MMS or MMK
  191        makefile.std     =>  Generic UNIX makefile (cc, creates static libpng.a)
  192        makefile.elf     =>  Linux/ELF makefile symbol versioning,
  193                             gcc, creates libpng12.so.0.1.2.12)
  194        makefile.linux   =>  Linux/ELF makefile
  195                             (gcc, creates libpng12.so.0.1.2.12)
  196        makefile.gcmmx   =>  Linux/ELF makefile
  197                             (gcc, creates libpng12.so.0.1.2.12,
  198                             uses assembler code tuned for Intel MMX platform)
  199        makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)
  200        makefile.knr     =>  Archaic UNIX Makefile that converts files with
  201                             ansi2knr (Requires ansi2knr.c from
  202                             ftp://ftp.cs.wisc.edu/ghost)
  203        makefile.aix     =>  AIX makefile
  204        makefile.cygwin  =>  Cygwin/gcc makefile
  205        makefile.darwin  =>  Darwin makefile
  206        makefile.dec     =>  DEC Alpha UNIX makefile
  207        makefile.freebsd =>  FreeBSD makefile
  208        makefile.hpgcc   =>  HPUX makefile using gcc
  209        makefile.hpux    =>  HPUX (10.20 and 11.00) makefile
  210        makefile.hp64    =>  HPUX (10.20 and 11.00) makefile, 64 bit
  211        makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)
  212        makefile.intel   =>  Intel C/C++ version 4.0 and later
  213        libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later
  214        makefile.netbsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng.so.
  215        makefile.ne12bsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng12.so
  216        makefile.openbsd =>  OpenBSD makefile
  217        makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)
  218        makefile.sggcc   =>  Silicon Graphics
  219                             (gcc, creates libpng12.so.0.1.2.12)
  220        makefile.sunos   =>  Sun makefile
  221        makefile.solaris =>  Solaris 2.X makefile
  222                             (gcc, creates libpng12.so.0.1.2.12)
  223        makefile.so9     =>  Solaris 9 makefile
  224                             (gcc, creates libpng12.so.0.1.2.12)
  225        makefile.32sunu  =>  Sun Ultra 32-bit makefile
  226        makefile.64sunu  =>  Sun Ultra 64-bit makefile
  227        makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc
  228        makefile.mips    =>  MIPS makefile
  229        makefile.acorn   =>  Acorn makefile
  230        makefile.amiga   =>  Amiga makefile
  231        smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC
  232                             compiler (Requires SCOPTIONS, copied from
  233                             scripts/SCOPTIONS.ppc)
  234        makefile.atari   =>  Atari makefile
  235        makefile.beos    =>  BEOS makefile for X86
  236        makefile.bor     =>  Borland makefile (uses bcc)
  237        makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)
  238        makefile.tc3     =>  Turbo C 3.0 makefile
  239        makefile.dj2     =>  DJGPP 2 makefile
  240        makefile.msc     =>  Microsoft C makefile
  241        makefile.vcawin32=>  makefile for Microsoft Visual C++ 5.0 and
  242                             later (uses assembler code tuned for Intel MMX
  243                             platform)
  244        makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and
  245                             later (does not use assembler code)
  246        makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
  247        pngos2.def       =>  OS/2 module definition file used by makefile.os2
  248        makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model
  249        makevms.com      =>  VMS build script
  250        SCOPTIONS.ppc    =>  Used with smakefile.ppc
  251 
  252 Good luck, and happy coding.
  253 
  254 -Glenn Randers-Pehrson (current maintainer)
  255  Internet: glennrp at users.sourceforge.net
  256 
  257 -Andreas Eric Dilger (former maintainer, 1996-1997)
  258  Internet: adilger at enel.ucalgary.ca
  259  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
  260 
  261 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
  262  (formerly of Group 42, Inc)
  263  Internet: gschal at infinet.com