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      1 README for libpng version 1.6.10 - March 6, 2014 (shared library 16.0)
      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 or
      7 libpng-*.tar.xz or if you want UNIX-style line endings in the text files,
      8 or lpng*.7z 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 and not on material submitted
     58 privately to Guy, Andreas, or Glenn.  They will forward any good
     59 suggestions to the list.
     60 
     61 For a detailed description on using libpng, read libpng-manual.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 zlib.net.
     81 
     82 You may also want a copy of the PNG specification.  It is available
     83 as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find
     84 these at http://www.libpng.org/pub/png/documents/
     85 
     86 This code is currently being archived at libpng.sf.net in the
     87 [DOWNLOAD] area, and at ftp://ftp.simplesystems.org.  If you can't find it
     88 in any of those places, e-mail me, and I'll help you find it.
     89 
     90 If you have any code changes, requests, problems, etc., please e-mail
     91 them to me.  Also, I'd appreciate any make files or project files,
     92 and any modifications you needed to make to get libpng to compile,
     93 along with a #define variable to tell what compiler/system you are on.
     94 If you needed to add transformations to libpng, or wish libpng would
     95 provide the image in a different way, drop me a note (and code, if
     96 possible), so I can consider supporting the transformation.
     97 Finally, if you get any warning messages when compiling libpng
     98 (note: not zlib), and they are easy to fix, I'd appreciate the
     99 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
    100 
    101 This release was created and will be supported by myself (of course
    102 based in a large way on Guy's and Andreas' earlier work), and the PNG
    103 development group.
    104 
    105 Send comments/corrections/commendations to png-mng-implement at
    106 lists.sourceforge.net (subscription required; visit
    107 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
    108 to subscribe) or to glennrp at users.sourceforge.net
    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
    112 read mail addressed to the png-implement list, however.
    113 
    114 Please do not send general questions about PNG.  Send them to
    115 png-mng-misc at lists.sf.net (subscription required; visit
    116 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
    117 subscribe).  If you have a question about something
    118 in the PNG specification that is related to using libpng, send it
    119 to me.  Send me any questions that start with "I was using libpng,
    120 and ...".  If in doubt, send questions to me.  I'll bounce them
    121 to others, if necessary.
    122 
    123 Please do not send suggestions on how to change PNG.  We have
    124 been discussing PNG for nineteen years now, and it is official and
    125 finished.  If you have suggestions for libpng, however, I'll
    126 gladly listen.  Even if your suggestion is not used immediately,
    127 it may be used later.
    128 
    129 Files in this distribution:
    130 
    131       ANNOUNCE      =>  Announcement of this version, with recent changes
    132       CHANGES       =>  Description of changes between libpng versions
    133       KNOWNBUG      =>  List of known bugs and deficiencies
    134       LICENSE       =>  License to use and redistribute libpng
    135       README        =>  This file
    136       TODO          =>  Things not implemented in the current library
    137       Y2KINFO       =>  Statement of Y2K compliance
    138       example.c     =>  Example code for using libpng functions
    139       libpng.3      =>  manual page for libpng (includes libpng-manual.txt)
    140       libpng-manual.txt  =>  Description of libpng and its functions
    141       libpngpf.3    =>  manual page for libpng's private functions
    142       png.5         =>  manual page for the PNG format
    143       png.c         =>  Basic interface functions common to library
    144       png.h         =>  Library function and interface declarations (public)
    145       pngpriv.h     =>  Library function and interface declarations (private)
    146       pngconf.h     =>  System specific library configuration (public)
    147       pngstruct.h   =>  png_struct declaration (private)
    148       pnginfo.h     =>  png_info struct declaration (private)
    149       pngdebug.h    =>  debugging macros (private)
    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       arm           =>  Contains optimized code for the ARM platform
    169       contrib       =>  Contributions
    170        examples         =>  Example programs
    171        gregbook         =>  source code for PNG reading and writing, from
    172                             Greg Roelofs' "PNG: The Definitive Guide",
    173                             O'Reilly, 1999
    174        libtests         =>  Test programs
    175        pngminim         =>  Minimal decoder, encoder, and progressive decoder
    176                             programs demonstrating use of pngusr.dfa
    177        pngminus         =>  Simple pnm2png and png2pnm programs
    178        pngsuite         =>  Test images
    179        tools            =>  Various tools
    180        visupng      =>  Contains a MSVC workspace for VisualPng
    181       projects      =>  Contains project files and workspaces for
    182                         building a DLL
    183        owatcom          =>  Contains a WATCOM project for building libpng
    184        visualc71        =>  Contains a Microsoft Visual C++ (MSVC)
    185                             workspace for building libpng and zlib
    186        vstudio          =>  Contains a Microsoft Visual C++ (MSVC)
    187                             workspace for building libpng and zlib
    188       scripts       =>  Directory containing scripts for building libpng:
    189                             (see scripts/README.txt for the list of scripts)
    190 
    191 Good luck, and happy coding.
    192 
    193 -Glenn Randers-Pehrson (current maintainer, since 1998)
    194  Internet: glennrp at users.sourceforge.net
    195 
    196 -Andreas Eric Dilger (former maintainer, 1996-1997)
    197  Internet: adilger at enel.ucalgary.ca
    198  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
    199 
    200 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
    201  (formerly of Group 42, Inc)
    202  Internet: gschal at infinet.com
    203