-README for libpng version 1.6.13 - August 21, 2014 (shared library 16.0)
-See the note about version numbers near the top of png.h
+README for libpng version 1.6.40
+================================
-See INSTALL for instructions on how to install libpng.
+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.
+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.
+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`.
-****
-Note that some of the changes to the png_info structure render this
+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 https://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 and commendations to `png-mng-implement`
+at `lists.sourceforge.net`. (Subscription is 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 is required; visit
+https://lists.sourceforge.net/lists/listinfo/png-mng-misc
+to subscribe.)
+
+Historical notes
+----------------
+
+The libpng library has been in extensive use and testing since mid-1995.
+Version 0.89, published a year later, was the first official release.
+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 below 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.
+`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,
+To avoid problems with changes to the internals of the `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
+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
+It is important to note that the APIs did 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.
+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.
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
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.
-
-I am not a lawyer, but I believe that the Export Control Classification
-Number (ECCN) for libpng is EAR99, which means not subject to export
-controls or International Traffic in Arms Regulations (ITAR) because it
-is open source, publicly available software, that does not contain any
-encryption software. See the EAR, paragraphs 734.3(b)(3) and 734.7(b).
-
-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
+The 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 included 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-to-8 bit color
+conversion. Some of these experimental functions, such as the weighted
+filter heuristics, have since been removed.
+
+Files included 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/ => Examples of libpng usage
+ 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.)
projects / platform / upstream / libpng.git / blobdiff