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 README for libpng version 1.6.10 - March 6, 2014 (shared library 16.0)

 See the note about version numbers near the top of png.h

 See INSTALL for instructions on how to install libpng.

 Libpng comes in several distribution formats.  Get libpng-*.tar.gz or

 libpng-*.tar.xz or if you want UNIX-style line endings in the text files,

 or lpng*.7z or lpng*.zip if you want DOS-style line endings.

 Version 0.89 was the first official release of libpng.  Don't let the

 fact that it's the first release fool you.  The libpng library has been in

 extensive use and testing since mid-1995.  By late 1997 it had

 finally gotten to the stage where there hadn't been significant

 changes to the API in some time, and people have a bad feeling about

 libraries with versions < 1.0.  Version 1.0.0 was released in

 March 1998.

 ****

 Note that some of the changes to the png_info structure render this

 version of the library binary incompatible with libpng-0.89 or

 earlier versions if you are using a shared library.  The type of the

 "filler" parameter for png_set_filler() has changed from png_byte to

 png_uint_32, which will affect shared-library applications that use

 this function.

 To avoid problems with changes to the internals of png_info_struct,

 new APIs have been made available in 0.95 to avoid direct application

 access to info_ptr.  These functions are the png_set_<chunk> and

 png_get_<chunk> functions.  These functions should be used when

 accessing/storing the info_struct data, rather than manipulating it

 directly, to avoid such problems in the future.

 It is important to note that the APIs do not make current programs

 that access the info struct directly incompatible with the new

 library.  However, it is strongly suggested that new programs use

 the new APIs (as shown in example.c and pngtest.c), and older programs

 be converted to the new format, to facilitate upgrades in the future.

 ****

 Additions since 0.90 include the ability to compile libpng as a

 Windows DLL, and new APIs for accessing data in the info struct.

 Experimental functions include the ability to set weighting and cost

 factors for row filter selection, direct reads of integers from buffers

 on big-endian processors that support misaligned data access, faster

 methods of doing alpha composition, and more accurate 16->8 bit color

 conversion.

 The additions since 0.89 include the ability to read from a PNG stream

 which has had some (or all) of the signature bytes read by the calling

 application.  This also allows the reading of embedded PNG streams that

 do not have the PNG file signature.  As well, it is now possible to set

 the library action on the detection of chunk CRC errors.  It is possible

 to set different actions based on whether the CRC error occurred in a

 critical or an ancillary chunk.

 The changes made to the library, and bugs fixed are based on discussions

 on the PNG-implement mailing list and not on material submitted

 privately to Guy, Andreas, or Glenn.  They will forward any good

 suggestions to the list.

 For a detailed description on using libpng, read libpng-manual.txt.  For

 examples of libpng in a program, see example.c and pngtest.c.  For usage

 information and restrictions (what little they are) on libpng, see

 png.h.  For a description on using zlib (the compression library used by

 libpng) and zlib's restrictions, see zlib.h

 I have included a general makefile, as well as several machine and

 compiler specific ones, but you may have to modify one for your own needs.

 You should use zlib 1.0.4 or later to run this, but it MAY work with

 versions as old as zlib 0.95.  Even so, there are bugs in older zlib

 versions which can cause the output of invalid compression streams for

 some images.  You will definitely need zlib 1.0.4 or later if you are

 taking advantage of the MS-DOS "far" structure allocation for the small

 and medium memory models.  You should also note that zlib is a

 compression library that is useful for more things than just PNG files.

 You can use zlib as a drop-in replacement for fread() and fwrite() if

 you are so inclined.

 zlib should be available at the same place that libpng is, or at zlib.net.

 You may also want a copy of the PNG specification.  It is available

 as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find

 these at http://www.libpng.org/pub/png/documents/

 This code is currently being archived at libpng.sf.net in the

 [DOWNLOAD] area, and at ftp://ftp.simplesystems.org.  If you can't find it

 in any of those places, e-mail me, and I'll help you find it.

 If you have any code changes, requests, problems, etc., please e-mail

 them to me.  Also, I'd appreciate any make files or project files,

 and any modifications you needed to make to get libpng to compile,

 along with a #define variable to tell what compiler/system you are on.

 If you needed to add transformations to libpng, or wish libpng would

 provide the image in a different way, drop me a note (and code, if

 possible), so I can consider supporting the transformation.

 Finally, if you get any warning messages when compiling libpng

 (note: not zlib), and they are easy to fix, I'd appreciate the

 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.

 This release was created and will be supported by myself (of course

 based in a large way on Guy's and Andreas' earlier work), and the PNG

 development group.

 Send comments/corrections/commendations to png-mng-implement at

 lists.sourceforge.net (subscription required; visit

 https://lists.sourceforge.net/lists/listinfo/png-mng-implement

 to subscribe) or to glennrp at users.sourceforge.net

 You can't reach Guy, the original libpng author, at the addresses

 given in previous versions of this document.  He and Andreas will

 read mail addressed to the png-implement list, however.

 Please do not send general questions about PNG.  Send them to

 png-mng-misc at lists.sf.net (subscription required; visit

 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to

 subscribe).  If you have a question about something

 in the PNG specification that is related to using libpng, send it

 to me.  Send me any questions that start with "I was using libpng,

 and ...".  If in doubt, send questions to me.  I'll bounce them

 to others, if necessary.

 Please do not send suggestions on how to change PNG.  We have

 been discussing PNG for nineteen years now, and it is official and

 finished.  If you have suggestions for libpng, however, I'll

 gladly listen.  Even if your suggestion is not used immediately,

 it may be used later.

 Files in this distribution:

       ANNOUNCE      =>  Announcement of this version, with recent changes

       CHANGES       =>  Description of changes between libpng versions

       KNOWNBUG      =>  List of known bugs and deficiencies

       LICENSE       =>  License to use and redistribute libpng

       README        =>  This file

       TODO          =>  Things not implemented in the current library

       Y2KINFO       =>  Statement of Y2K compliance

       example.c     =>  Example code for using libpng functions

       libpng.3      =>  manual page for libpng (includes libpng-manual.txt)

       libpng-manual.txt  =>  Description of libpng and its functions

       libpngpf.3    =>  manual page for libpng's private functions

       png.5         =>  manual page for the PNG format

       png.c         =>  Basic interface functions common to library

       png.h         =>  Library function and interface declarations (public)

       pngpriv.h     =>  Library function and interface declarations (private)

       pngconf.h     =>  System specific library configuration (public)

       pngstruct.h   =>  png_struct declaration (private)

       pnginfo.h     =>  png_info struct declaration (private)

       pngdebug.h    =>  debugging macros (private)

       pngerror.c    =>  Error/warning message I/O functions

       pngget.c      =>  Functions for retrieving info from struct

       pngmem.c      =>  Memory handling functions

       pngbar.png    =>  PNG logo, 88x31

       pngnow.png    =>  PNG logo, 98x31

       pngpread.c    =>  Progressive reading functions

       pngread.c     =>  Read data/helper high-level functions

       pngrio.c      =>  Lowest-level data read I/O functions

       pngrtran.c    =>  Read data transformation functions

       pngrutil.c    =>  Read data utility functions

       pngset.c      =>  Functions for storing data into the info_struct

       pngtest.c     =>  Library test program

       pngtest.png   =>  Library test sample image

       pngtrans.c    =>  Common data transformation functions

       pngwio.c      =>  Lowest-level write I/O functions

       pngwrite.c    =>  High-level write functions

       pngwtran.c    =>  Write data transformations

       pngwutil.c    =>  Write utility functions

       arm           =>  Contains optimized code for the ARM platform

       contrib       =>  Contributions

        examples         =>  Example programs

        gregbook         =>  source code for PNG reading and writing, from

                             Greg Roelofs' "PNG: The Definitive Guide",

                             O'Reilly, 1999

        libtests         =>  Test programs

        pngminim         =>  Minimal decoder, encoder, and progressive decoder

                             programs demonstrating use of pngusr.dfa

        pngminus         =>  Simple pnm2png and png2pnm programs

        pngsuite         =>  Test images

        tools            =>  Various tools

        visupng      =>  Contains a MSVC workspace for VisualPng

       projects      =>  Contains project files and workspaces for

                         building a DLL

        owatcom          =>  Contains a WATCOM project for building libpng

        visualc71        =>  Contains a Microsoft Visual C++ (MSVC)

                             workspace for building libpng and zlib

        vstudio          =>  Contains a Microsoft Visual C++ (MSVC)

                             workspace for building libpng and zlib

       scripts       =>  Directory containing scripts for building libpng:

                             (see scripts/README.txt for the list of scripts)

 Good luck, and happy coding.

 -Glenn Randers-Pehrson (current maintainer, since 1998)

  Internet: glennrp at users.sourceforge.net

 -Andreas Eric Dilger (former maintainer, 1996-1997)

  Internet: adilger at enel.ucalgary.ca

  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/

 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)

  (formerly of Group 42, Inc)

  Internet: gschal at infinet.com