README for libpng version 1.5.4 - July 7, 2011 (shared library 15.0) | |
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, | |
libpng-*.tar.xz or libpng-*.tar.bz2 if you want UNIX-style line endings | |
in the text files, 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 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 do 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. | |
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 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. | |
ftp://ftp.info-zip.org/pub/infozip/zlib | |
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 on CompuServe, Lib 20 (PNG SUPPORT) | |
at GO GRAPHSUP. If you can't find it in any of those places, | |
e-mail me, and I'll help you find it. | |
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 sixteen 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 | |
contrib => Contributions | |
gregbook => source code for PNG reading and writing, from | |
Greg Roelofs' "PNG: The Definitive Guide", | |
O'Reilly, 1999 | |
msvctest => Builds and runs pngtest using a MSVC workspace | |
pngminus => Simple pnm2png and png2pnm programs | |
pngsuite => Test images | |
visupng => Contains a MSVC workspace for VisualPng | |
projects => Contains project files and workspaces for | |
building a DLL | |
cbuilder5 => Contains a Borland workspace for building | |
libpng and zlib | |
visualc6 => Contains a Microsoft Visual C++ (MSVC) | |
workspace for building libpng and zlib | |
visualc71 => Contains a Microsoft Visual C++ (MSVC) | |
workspace for building libpng and zlib | |
xcode => Contains an Apple xcode | |
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 |