180 lines
8.3 KiB
Plaintext
180 lines
8.3 KiB
Plaintext
README for libpng 1.10
|
|
|
|
This 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 for about two years. However, it's
|
|
finally gotten to the stage where there haven't been significant
|
|
changes to the API in some time, and people have a bad feeling about
|
|
libraries with versions < 1.0.
|
|
|
|
Note that the version number is 1.10 to avoid potential problems
|
|
with shared libraries created for Linux ELF under version 0.89,
|
|
which mistakenly used 1.0.89 as the library version number in
|
|
false anticipation of an imminent 1.0 release.
|
|
|
|
****
|
|
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 which 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
|
|
which 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 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 implementation mailing list <png-implement@dworking.wustl.edu>
|
|
and not on material submitted to Guy.
|
|
|
|
For a detailed description on using libpng, read libpng.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.
|
|
If not, it should be at ftp.uu.net in /graphics/png
|
|
Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib
|
|
|
|
You may also want a copy of the PNG specification. It is available
|
|
as an Internet Draft, and RFC, and a W3C Recommendation. Failing
|
|
these resources you can try ftp.uu.net in the /graphics/png directory.
|
|
|
|
This code is currently being archived at ftp.uu.net in the
|
|
/graphics/png directory, 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 earlier work), and the PNG group.
|
|
|
|
adilger@enel.ucalgary.ca
|
|
png-implement@dworkin.wustl.edu
|
|
|
|
You can reach Guy, the original libpng author, at (internet preferred):
|
|
|
|
internet: schalnat@group42.com
|
|
CompuServe: 75501,1625
|
|
|
|
Please do not send general questions about PNG. Send them to
|
|
the address in the specification. At the same time, please do
|
|
not send libpng questions to that address, send them to me. I'll
|
|
get them in the end anyway. 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 a couple 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 for version
|
|
1.0, it may be used later.
|
|
|
|
Files in this distribution:
|
|
|
|
CHANGES => Description of changes between libpng versions
|
|
README => This file
|
|
TODO => Things not implemented in the current library
|
|
ansi2knr.c => Converts files to K&R style function declarations
|
|
build.bat => MS-DOS batch file for Borland compiler
|
|
descrip.mms => VMS project file
|
|
example.c => Example code for using libpng functions
|
|
libpng.txt => Description of libpng and its functions
|
|
makefile => Default Unixish makefile
|
|
makefile.aco => ACORN makefile
|
|
makefile.ama => Amiga makefile
|
|
makefile.atr => Atari makefile
|
|
makefile.bor => Borland makefile
|
|
makefile.dj2 => DJGPP 2 makefile
|
|
makefile.elf => Unix ELF makefile
|
|
makefile.knr => Makefile which calls ansi2knr to convert files
|
|
makefile.mip => MIPS makefile
|
|
makefile.msc => Microsoft C makefile
|
|
makefile.std => Standard Unix makefile
|
|
makefile.tc => Turbo C makefile
|
|
makevms.com => VMS make program
|
|
png.c => Basic interface functions common to library
|
|
png.h => Library function and interface declarations
|
|
pngconf.h => System specific library configuration
|
|
pngerror.c => Error/warning message I/O functions
|
|
pngmem.c => Memory handling functions
|
|
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
|
|
|
|
Good luck, and happy coding.
|
|
|
|
-Andreas Eric Dilger
|
|
Internet: adilger@enel.ucalgary.ca
|
|
Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
|
|
|
|
-Guy Eric Schalnat
|
|
Group 42, Inc.
|
|
Internet: schalnat@group42.com
|
|
CompuServe: 75501,1625
|
|
Web: http://www.group42.com/
|
|
|