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      1 README for libpng version 1.2.46 - July 9, 2011 (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.xz, 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.xz 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 and not on material submitted
     62 privately to Guy, Andreas, or Glenn.  They will forward any good
     63 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
    109 development group.
    110 
    111 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
    112 (subscription required; visit 
    113 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
    114 to subscribe) or to glennrp at users.sourceforge.net
    115 
    116 You can't reach Guy, the original libpng author, at the addresses
    117 given in previous versions of this document.  He and Andreas will
    118 read mail addressed to the png-mng-implement list, however.
    119 
    120 Please do not send general questions about PNG.  Send them to
    121 the (png-mng-misc at lists.sourceforge.net, subscription required, visit
    122 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
    123 subscribe). On the other hand, please do not send libpng questions to
    124 that address, send them to me 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        pngminim     =>  Simple pnm2pngm and png2pnmm programs
    179        pngminus     =>  Simple pnm2png and png2pnm programs
    180        pngsuite     =>  Test images
    181        visupng      =>  Contains a MSVC workspace for VisualPng
    182       projects      =>  Contains project files and workspaces for
    183                         building a DLL
    184        beos             =>  Contains a Beos workspace for building libpng
    185        c5builder        =>  Contains a Borland workspace for building
    186                             libpng and zlib
    187        netware.txt      =>  Contains instructions for downloading a set
    188                             of project files for building libpng and
    189                             zlib on Netware.
    190        visualc6         =>  Contains a Microsoft Visual C++ (MSVC)
    191                             workspace for building libpng and zlib
    192        wince.txt        =>  Contains instructions for downloading a
    193                             Microsoft Visual C++ (Windows CD Toolkit)
    194                             workspace for building libpng and zlib on
    195                             WindowsCE
    196        xcode            =>  Contains xcode project files
    197       scripts       =>  Directory containing scripts for building libpng:
    198        descrip.mms      =>  VMS makefile for MMS or MMK
    199        makefile.std     =>  Generic UNIX makefile (cc, creates static
    200                             libpng.a)
    201        makefile.elf     =>  Linux/ELF gcc makefile symbol versioning,
    202                             creates libpng12.so.0.1.2.46)
    203        makefile.linux   =>  Linux/ELF makefile (gcc, creates
    204                             libpng12.so.0.1.2.46)
    205        makefile.gcmmx   =>  Linux/ELF makefile (gcc, creates
    206                             libpng12.so.0.1.2.46, previously
    207                             used assembler code tuned for Intel MMX
    208                             platform)
    209        makefile.gcc     =>  Generic makefile (gcc, creates static
    210                             libpng.a)
    211        makefile.knr     =>  Archaic UNIX Makefile that converts files
    212                             with ansi2knr (Requires ansi2knr.c from
    213                             ftp://ftp.cs.wisc.edu/ghost)
    214        makefile.aix     =>  AIX makefile
    215        makefile.cygwin  =>  Cygwin/gcc makefile
    216        makefile.darwin  =>  Darwin makefile
    217        makefile.dec     =>  DEC Alpha UNIX makefile
    218        makefile.freebsd =>  FreeBSD makefile
    219        makefile.hpgcc   =>  HPUX makefile using gcc
    220        makefile.hpux    =>  HPUX (10.20 and 11.00) makefile
    221        makefile.hp64    =>  HPUX (10.20 and 11.00) makefile, 64 bit
    222        makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2
    223                             (static)
    224        makefile.intel   =>  Intel C/C++ version 4.0 and later
    225        libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later
    226        makefile.netbsd  =>  NetBSD/cc makefile, makes libpng.so.
    227        makefile.ne12bsd  =>  NetBSD/cc makefile, makes libpng12.so
    228        makefile.openbsd =>  OpenBSD makefile
    229        makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)
    230        makefile.sggcc   =>  Silicon Graphics
    231                             (gcc, creates libpng12.so.0.1.2.46)
    232        makefile.sunos   =>  Sun makefile
    233        makefile.solaris =>  Solaris 2.X makefile
    234                             (gcc, creates libpng12.so.0.1.2.46)
    235        makefile.so9     =>  Solaris 9 makefile
    236                             (gcc, creates libpng12.so.0.1.2.46)
    237        makefile.32sunu  =>  Sun Ultra 32-bit makefile
    238        makefile.64sunu  =>  Sun Ultra 64-bit makefile
    239        makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc
    240        makefile.mips    =>  MIPS makefile
    241        makefile.acorn   =>  Acorn makefile
    242        makefile.amiga   =>  Amiga makefile
    243        smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC
    244                             compiler (Requires SCOPTIONS, copied from
    245                             scripts/SCOPTIONS.ppc)
    246        makefile.atari   =>  Atari makefile
    247        makefile.beos    =>  BEOS makefile for X86
    248        makefile.bor     =>  Borland makefile (uses bcc)
    249        makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)
    250        makefile.tc3     =>  Turbo C 3.0 makefile
    251        makefile.dj2     =>  DJGPP 2 makefile
    252        makefile.msc     =>  Microsoft C makefile
    253        makefile.vcawin32=>  makefile for Microsoft Visual C++ 5.0 and
    254                             later (previously used assembler code tuned
    255                             for Intel MMX platform)
    256        makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and
    257                             later (does not use assembler code)
    258        makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
    259        pngos2.def       =>  OS/2 module definition file used by makefile.os2
    260        makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model
    261        makevms.com      =>  VMS build script
    262        SCOPTIONS.ppc    =>  Used with smakefile.ppc
    263 
    264 Good luck, and happy coding.
    265 
    266 -Glenn Randers-Pehrson (current maintainer, since 1998)
    267  Internet: glennrp at users.sourceforge.net
    268 
    269 -Andreas Eric Dilger (former maintainer, 1996-1997)
    270  Internet: adilger at enel.ucalgary.ca
    271  Web: http://members.shaw.ca/adilger/
    272 
    273 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
    274  (formerly of Group 42, Inc)
    275  Internet: gschal at infinet.com
    276