2024-02-24 12:41:29 +08:00
|
|
|
README for libpng version 1.6.43
|
2023-12-08 00:13:39 +08:00
|
|
|
================================
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
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`.
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
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
|
|
|
|
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.
|
|
|
|
|
|
|
|
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 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
|
2024-02-24 12:41:29 +08:00
|
|
|
arm/ => Optimized code for ARM Neon
|
|
|
|
intel/ => Optimized code for INTEL SSE2
|
|
|
|
loongarch/ => Optimized code for LoongArch LSX
|
|
|
|
mips/ => Optimized code for MIPS MSA and MIPS MMI
|
|
|
|
powerpc/ => Optimized code for PowerPC VSX
|
2023-12-08 00:13:39 +08:00
|
|
|
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
|
2024-02-24 12:41:29 +08:00
|
|
|
pngexif/ => Program to inspect the EXIF information in PNG files
|
2023-12-08 00:13:39 +08:00
|
|
|
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.)
|