text: README for libpng version 1.6.7 - November 14, 2013 (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 eighteen 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
  