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+README for libpng version 1.6.39
+================================
+
+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 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 the 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 did not make current programs
+that access the info struct directly incompatible with the new
+library, through libpng-1.2.x. In libpng-1.4.x, which was meant to
+be a transitional release, members of the png_struct and the
+info_struct can still be accessed, but the compiler will issue a
+warning about deprecated usage. Since libpng-1.5.0, direct access
+to these structs is not allowed, and the definitions of the structs
+reside in private pngstruct.h and pnginfo.h header files that are not
+accessible to applications. 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.
+
+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 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
+https://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/pngdocs.html .
+
+This code is currently being archived at libpng.sourceforge.io in the
+[DOWNLOAD] area, and at http://libpng.download/src .
+
+This release, based in a large way on Glenn's, Guy's and Andreas'
+earlier work, was created and will be supported by myself 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).
+
+Send general questions about the PNG specification to png-mng-misc
+at lists.sourceforge.net (subscription required; visit
+https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
+subscribe).
+
+Files in this distribution:
+
+ ANNOUNCE => Announcement of this version, with recent changes
+ AUTHORS => List of contributing authors
+ CHANGES => Description of changes between libpng versions
+ INSTALL => Instructions to install libpng
+ LICENSE => License to use and redistribute libpng
+ README => This file
+ TODO => Things not implemented in the current library
+ TRADEMARK => Trademark information
+ 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 (deprecated)
+ 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/ => Optimized code for the ARM platform
+ intel/ => Optimized code for the INTEL-SSE2 platform
+ mips/ => Optimized code for the MIPS platform
+ powerpc/ => Optimized code for the PowerPC platform
+ ci/ => Scripts for continuous integration
+ contrib/ => External contributions
+ arm-neon/ => Optimized code for the ARM-NEON platform
+ mips-msa/ => Optimized code for the MIPS-MSA platform
+ powerpc-vsx/ => Optimized code for the POWERPC-VSX platform
+ examples/ => Example programs
+ gregbook/ => Source code for PNG reading and writing, from
+ "PNG: The Definitive Guide" by Greg Roelofs,
+ O'Reilly, 1999
+ libtests/ => Test programs
+ oss-fuzz/ => Files used by the OSS-Fuzz project for fuzz-testing
+ libpng
+ pngminim/ => Minimal decoder, encoder, and progressive decoder
+ programs demonstrating the use of pngusr.dfa
+ pngminus/ => Simple pnm2png and png2pnm programs
+ pngsuite/ => Test images
+ testpngs/ => Test images
+ tools/ => Various tools
+ visupng/ => VisualPng, a Windows viewer for PNG images
+ projects/ => Project files and workspaces for various IDEs
+ owatcom/ => OpenWatcom project
+ visualc71/ => Microsoft Visual C++ 7.1 workspace
+ vstudio/ => Microsoft Visual Studio workspace
+ scripts/ => Scripts and makefiles for building libpng
+ (see scripts/README.txt for the complete list)
+ tests/ => Test scripts
+
+Good luck, and happy coding!
+
+ * Cosmin Truta (current maintainer, since 2018)
+ * Glenn Randers-Pehrson (former maintainer, 1998-2018)
+ * Andreas Eric Dilger (former maintainer, 1996-1997)
+ * Guy Eric Schalnat (original author and former maintainer, 1995-1996)
+ (formerly of Group 42, Inc.)