diff options
Diffstat (limited to '')
| -rw-r--r-- | media/libpng/README | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/media/libpng/README b/media/libpng/README new file mode 100644 index 0000000000..cfc1f0e3dc --- /dev/null +++ b/media/libpng/README @@ -0,0 +1,183 @@ +README for libpng version 1.6.37 - April 14, 2019 +================================================= + +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 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 + 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 + 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 + 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 + powerpc => Contains optimized code for the PowerPC platform + contrib => Contributions + arm-neon => Optimized code for ARM-NEON platform + powerpc-vsx => Optimized code for POWERPC-VSX platform + examples => Example programs + gregbook => source code for PNG reading and writing, from + Greg Roelofs' "PNG: The Definitive Guide", + O'Reilly, 1999 + libtests => Test programs + mips-msa => Optimized code for MIPS-MSA platform + pngminim => Minimal decoder, encoder, and progressive decoder + programs demonstrating use of pngusr.dfa + pngminus => Simple pnm2png and png2pnm programs + pngsuite => Test images + testpngs + tools => Various tools + visupng => Contains a MSVC workspace for VisualPng + intel => Optimized code for INTEL-SSE2 platform + mips => Optimized code for MIPS platform + 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! + + * 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.) |