mewin/libpng
1
0
Fork 0
mirror of https://git.code.sf.net/p/libpng/code.git synced 2025-07-10 18:04:09 +02:00
Code Issues Projects Releases Wiki Activity

Reorganize and update the README file; add Markdown formatting

Browse Source
This commit is contained in:
Cosmin Truta 2022-11-27 16:20:31 +02:00
parent 3c761b5135
commit b126f80710
1 changed files with 79 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

160
README
View File

@ -1,57 +1,88 @@
README for libpng version 1.6.40.git README for libpng version 1.6.40.git
==================================== ====================================
See the note about version numbers near the top of png.h. See the note about version numbers near the top of `png.h`.
See INSTALL for instructions on how to install libpng. See `INSTALL` for instructions on how to install libpng.
Libpng comes in several distribution formats. Get libpng-*.tar.gz or Libpng comes in several distribution formats. Get `libpng-*.tar.gz`
libpng-*.tar.xz if you want UNIX-style line endings in the text files, or `libpng-*.tar.xz` if you want UNIX-style line endings in the text
or lpng*.7z or lpng*.zip if you want DOS-style line endings. 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 For a detailed description on using libpng, read `libpng-manual.txt`.
fact that it's the first release fool you. The libpng library has been For examples of libpng in a program, see `example.c` and `pngtest.c`.
in extensive use and testing since mid-1995. By late 1997 it had For usage information and restrictions (what little they are) on libpng,
finally gotten to the stage where there hadn't been significant see `png.h`. For a description on using zlib (the compression library
changes to the API in some time, and people have a bad feeling about used by libpng) and zlib's restrictions, see `zlib.h`.
libraries with versions < 1.0. Version 1.0.0 was released in
March 1998.
**** You should use zlib 1.0.4 or later to run this, but it _may_ work with
Note that some of the changes to the png_info structure render this 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 version of the library binary incompatible with libpng-0.89 or
earlier versions if you are using a shared library. The type of the 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 `filler` parameter for `png_set_filler()` has changed from `png_byte`
png_uint_32, which will affect shared-library applications that use to `png_uint_32`, which will affect shared-library applications that
this function. use this function.
To avoid problems with changes to the internals of the 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 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 access to `info_ptr`. These functions are the `png_set_<chunk>` and
png_get_<chunk> functions. These functions should be used when `png_get_<chunk>` functions. These functions should be used when
accessing/storing the info_struct data, rather than manipulating it accessing/storing the `info_struct` data, rather than manipulating it
directly, to avoid such problems in the future. directly, to avoid such problems in the future.
It is important to note that the APIs did 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 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 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 be a transitional release, members of the `png_struct` and the
info_struct can still be accessed, but the compiler will issue a `info_struct` can still be accessed, but the compiler will issue a
warning about deprecated usage. Since libpng-1.5.0, direct access warning about deprecated usage. Since libpng-1.5.0, direct access
to these structs is not allowed, and the definitions of the structs 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 reside in private `pngstruct.h` and `pnginfo.h` header files that are
accessible to applications. It is strongly suggested that new not accessible to applications. It is strongly suggested that new
programs use the new APIs (as shown in example.c and pngtest.c), and programs use the new APIs (as shown in `example.c` and `pngtest.c`),
older programs be converted to the new format, to facilitate upgrades and older programs be converted to the new format, to facilitate
in the future. 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 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 which has had some (or all) of the signature bytes read by the calling
@ -61,50 +92,17 @@ 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 to set different actions based on whether the CRC error occurred in a
critical or an ancillary chunk. critical or an ancillary chunk.
For a detailed description on using libpng, read libpng-manual.txt. The additions since 0.90 include the ability to compile libpng as a
For examples of libpng in a program, see example.c and pngtest.c. For Windows DLL, and new APIs for accessing data in the `info_struct`.
usage information and restrictions (what little they are) on libpng, Experimental functions included the ability to set weighting and cost
see png.h. For a description on using zlib (the compression library factors for row filter selection, direct reads of integers from buffers
used by libpng) and zlib's restrictions, see zlib.h 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.
I have included a general makefile, as well as several machine and Files included in this distribution
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 ANNOUNCE => Announcement of this version, with recent changes
AUTHORS => List of contributing authors AUTHORS => List of contributing authors
@ -153,7 +151,7 @@ Files in this distribution:
arm-neon/ => Optimized code for the ARM-NEON platform arm-neon/ => Optimized code for the ARM-NEON platform
mips-msa/ => Optimized code for the MIPS-MSA platform mips-msa/ => Optimized code for the MIPS-MSA platform
powerpc-vsx/ => Optimized code for the POWERPC-VSX platform powerpc-vsx/ => Optimized code for the POWERPC-VSX platform
examples/ => Example programs examples/ => Examples of libpng usage
gregbook/ => Source code for PNG reading and writing, from gregbook/ => Source code for PNG reading and writing, from
"PNG: The Definitive Guide" by Greg Roelofs, "PNG: The Definitive Guide" by Greg Roelofs,
O'Reilly, 1999 O'Reilly, 1999