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Glenn Randers-Pehrson 1999-09-17 12:27:26 -05:00
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91
ANNOUNCE
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@ -1,53 +1,56 @@
Libpng 1.0.3 - January 14, 1999
Libpng 1.0.4 - September 17, 1999
This is a public release of libpng, intended for use in production codes.
Changes since the previous public release (1.0.2):
Changes since the last public release (1.0.3):
libpng-1.0.3:
Replaced and extended code that was removed from png_set_filler() in 1.0.1a.
Fixed a bug in png_do_filler() that made it fail to write filler bytes in
the left-most pixel of each row (Kevin Bracey).
Changed "static pngcharp tIME_string" to "static char tIME_string[30]"
in pngtest.c (Duncan Simpson).
Fixed a bug in pngtest.c that caused pngtest to try to write a tIME chunk
even when no tIME chunk was present in the source file.
Fixed a problem in pngrutil.c: gray_to_rgb didn't always work with 16-bit.
Fixed a problem in png_read_push_finish_row(), which would not skip some
passes that it should skip, for images that are less than 3 pixels high.
Interchanged the order of calls to png_do_swap() and png_do_shift()
in pngwtran.c (John Cromer).
Added #ifdef PNG_DEBUG/#endif surrounding use of PNG_DEBUG in png.h .
Changed "bad adaptive filter type" from error to warning in pngrutil.c .
Fixed a documentation error about default filtering with 8-bit indexed-color.
Separated the PNG_NO_STDIO macro into PNG_NO_STDIO and PNG_NO_CONSOLE_IO
(L. Peter Deutsch).
Added png_set_rgb_to_gray() and png_get_rgb_to_gray_status() functions.
Added png_get_copyright() and png_get_header_version() functions.
Revised comments on png_set_progressive_read_fn() in libpng.txt and example.c
Added information about debugging in libpng.txt and libpng.3 .
Changed "ln -sf" to "ln -s -f" in makefile.s2x, makefile.lnx, and makefile.sco.
Removed lines after Dynamic Dependencies" in makefile.aco .
Revised makefile.dec to make a shared library (Jeremie Petit).
Removed trailing blanks from all files.
Removed misplaced #endif and #ifdef PNG_NO_EXTERN near the end of png.h
Added "if" tests to silence complaints about unused png_ptr in png.h and png.c
Changed "check_if_png" function in example.c to return true (nonzero) if PNG.
Changed libpng.txt to demonstrate png_sig_cmp() instead of png_check_sig()
which is obsolete.
Added makefile.hux, for Hewlett Packard HPUX 10.20 and 11.00 (Jim Rice)
Added a statement of Y2K compliance in png.h, libpng.1, and Y2KINFO.
Added check for PNG_READ_INTERLACE_SUPPORTED in pngread.c; issue a warning
if an attempt is made to read an interlaced image when it's not supported.
Added check if png_ptr->trans is defined before free'ing it in pngread.c
Modified the Y2K statement to include versions back to version 0.71
Fixed a bug in the check for valid IHDR bit_depth/color_types in pngrutil.c
Modified makefile.wat (added -zp8 flag, ".symbolic", changed some comments)
Replaced leading blanks with tab characters in makefile.hux
Changed "dworkin.wustl.edu" to "ccrc.wustl.edu" in various documents.
Changed (float)red and (float)green to (double)red, (double)green
in png_set_rgb_to_gray() to avoid "promotion" problems in AIX.
Fixed a bug in pngconf.h that omitted <stdio.h> when PNG_DEBUG==0 (K Bracey).
Reformatted libpng.3 and libpngpf.3 with proper fonts (script by J. vanZandt).
Updated documentation to refer to the PNG-1.2 specification.
Removed ansi2knr.c and left pointers to the latest source for ansi2knr.c
in makefile.knr, INSTALL, and README (L. Peter Deutsch)
Fixed bugs in calculation of the length of rowbytes when adding alpha
channels to 16-bit images, in pngrtran.c (Chris Nokleberg)
Added function png_set_user_transform_info() to store user_transform_ptr,
user_depth, and user_channels into the png_struct, and a function
png_get_user_transform_ptr() to retrieve the pointer (Chris Nokleberg)
Added function png_set_empty_plte_permitted() to make libpng useable
in MNG applications.
Corrected the typedef for png_free_ptr in png.h (Jesse Jones).
Correct gamma with srgb is 45455 instead of 45000 in pngrutil.c, to be
consistent with PNG-1.2, and allow variance of 500 before complaining.
Added assembler code contributed by Intel in file pngvcrd.c and modified
makefile.w32 to use it (Nirav Chhatrapati, INTEL Corporation, Gilles Vollant)
Define PNG_USE_PNGVCRD in makefile.w32, to get MMX assembler code.
Changed "ln -s -f" to "ln -f -s" in the makefiles to make Solaris happy.
Added makefile.beo for BEOS on X86, contributed by Sander Stok.
Replaced 2147483647L several places with PNG_MAX_UINT macro, defined in png.h
Changed leading blanks to tabs in all makefiles.
Made alternate versions of png_set_expand() in pngrtran.c, namely
png_set_gray_1_2_4_to_8, png_set_palette_to_rgb, and png_set_tRNS_to_alpha
(Greg Roelofs, in "PNG: The Definitive Guide").
Relocated start of 'extern "C"' block in png.h so it doesn't include pngconf.h
Revised calculation of num_blocks in pngmem.c to avoid a potentially
negative shift distance, whose results are undefined in the C language.
Added a check in pngset.c to prevent writing multiple tIME chunks.
Added a check in pngwrite.c to detect invalid small window_bits sizes.
Added a demo read_user_transform_fn that examines the row filters in pngtest.c
Define PNG_ALWAYS_EXTERN in pngconf.h if __STDC__ is defined
Made several minor corrections to pngtest.c
Changed "hptr += 16L" to "hptr = hptr + 16L" in pngmem.c for Turbo 3.0
Send comments/corrections/commendations to
png-implement@dworkin.wustl.edu or to randeg@alumni.rpi.edu
png-implement@ccrc.wustl.edu or to randeg@alum.rpi.edu
Glenn R-P
Send comments/corrections/commendations to
png-implement@dworkin.wustl.edu or to randeg@alumni.rpi.edu
Glenn Randers-Pehrson
libpng maintainer
PNG Development Group

55
CHANGES
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@ -386,4 +386,57 @@ version 1.0.2a [January 6, 1999]
which is obsolete.
version 1.0.3 [January 14, 1999]
Added makefile.hux, for Hewlett Packard HPUX 10.20 and 11.00 (Jim Rice)
Added a statement of Y2K compliance in png.h, libpng.1, and Y2KINFO.
Added a statement of Y2K compliance in png.h, libpng.3, and Y2KINFO.
version 1.0.3a [August 12, 1999]
Added check for PNG_READ_INTERLACE_SUPPORTED in pngread.c; issue a warning
if an attempt is made to read an interlaced image when it's not supported.
Added check if png_ptr->trans is defined before free'ing it in pngread.c
Modified the Y2K statement to include versions back to version 0.71
Fixed a bug in the check for valid IHDR bit_depth/color_types in pngrutil.c
Modified makefile.wat (added -zp8 flag, ".symbolic", changed some comments)
Replaced leading blanks with tab characters in makefile.hux
Changed "dworkin.wustl.edu" to "ccrc.wustl.edu" in various documents.
Changed (float)red and (float)green to (double)red, (double)green
in png_set_rgb_to_gray() to avoid "promotion" problems in AIX.
Fixed a bug in pngconf.h that omitted <stdio.h> when PNG_DEBUG==0 (K Bracey).
Reformatted libpng.3 and libpngpf.3 with proper fonts (script by J. vanZandt).
Updated documentation to refer to the PNG-1.2 specification.
Removed ansi2knr.c and left pointers to the latest source for ansi2knr.c
in makefile.knr, INSTALL, and README (L. Peter Deutsch)
Fixed bugs in calculation of the length of rowbytes when adding alpha
channels to 16-bit images, in pngrtran.c (Chris Nokleberg)
Added function png_set_user_transform_info() to store user_transform_ptr,
user_depth, and user_channels into the png_struct, and a function
png_get_user_transform_ptr() to retrieve the pointer (Chris Nokleberg)
Added function png_set_empty_plte_permitted() to make libpng useable
in MNG applications.
Corrected the typedef for png_free_ptr in png.h (Jesse Jones).
Correct gamma with srgb is 45455 instead of 45000 in pngrutil.c, to be
consistent with PNG-1.2, and allow variance of 500 before complaining.
Added assembler code contributed by Intel in file pngvcrd.c and modified
makefile.w32 to use it (Nirav Chhatrapati, INTEL Corporation, Gilles Vollant)
Changed "ln -s -f" to "ln -f -s" in the makefiles to make Solaris happy.
Added some aliases for png_set_expand() in pngrtran.c, namely
png_set_expand_PLTE(), png_set_expand_depth(), and png_set_expand_tRNS()
(Greg Roelofs, in "PNG: The Definitive Guide").
Added makefile.beo for BEOS on X86, contributed by Sander Stok.
version 1.0.3b [August 26, 1999]
Replaced 2147483647L several places with PNG_MAX_UINT macro, defined in png.h
Changed leading blanks to tabs in all makefiles.
Define PNG_USE_PNGVCRD in makefile.w32, to get MMX assembler code.
Made alternate versions of png_set_expand() in pngrtran.c, namely
png_set_gray_1_2_4_to_8, png_set_palette_to_rgb, and png_set_tRNS_to_alpha
(Greg Roelofs, in "PNG: The Definitive Guide"). Deleted the 1.0.3a aliases.
Relocated start of 'extern "C"' block in png.h so it doesn't include pngconf.h
Revised calculation of num_blocks in pngmem.c to avoid a potentially
negative shift distance, whose results are undefined in the C language.
Added a check in pngset.c to prevent writing multiple tIME chunks.
Added a check in pngwrite.c to detect invalid small window_bits sizes.
version 1.0.3d [September 4, 1999]
Fixed type casting of igamma in pngrutil.c
Added new png_expand functions to scripts/pngdef.pas and pngos2.def
Added a demo read_user_transform_fn that examines the row filters in pngtest.c
version 1.0.4 [September 17, 1999]
Define PNG_ALWAYS_EXTERN in pngconf.h if __STDC__ is defined
Delete #define PNG_INTERNAL and include "png.h" from pngasmrd.h
Made several minor corrections to pngtest.c

12
INSTALL
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@ -1,5 +1,5 @@
Installing libpng version 1.0.3 - January 14, 1999
Installing libpng version 1.0.4 - September 17, 1999
Before installing libpng, you must first install zlib. zlib
can usually be found wherever you got libpng. zlib can be
@ -10,7 +10,7 @@ zlib.h and zconf.h include files that correspond to the
version of zlib that's installed.
You can rename the directories that you downloaded (they
might be called "libpng-1.0.3" or "lpng103" and "zlib-1.1.3"
might be called "libpng-1.0.4" or "lpng103" and "zlib-1.1.3"
or "zlib113") so that you have directories called "zlib" and "libpng".
Your directory structure should look like this:
@ -41,18 +41,21 @@ include
descrip.mms => VMS makefile for MMS or MMK
makefile.std => Generic UNIX makefile
makefile.knr => Archaic UNIX Makefile that converts files with ansi2knr
(Requires ansi2knr.c from ftp://ftp.cs.wisc.edu/ghost)
makefile.dec => DEC Alpha UNIX makefile
makefile.hux => HPUX (10.20 and 11.00) makefile
makefile.sgi => Silicon Graphics IRIX makefile
makefile.sun => Sun makefile
makefile.s2x => Solaris 2.X makefile (gcc, creates libpng.so.2.1.0)
makefile.lnx => Linux/ELF makefile (gcc, creates libpng.so.2.1.0)
makefile.s2x => Solaris 2.X makefile (gcc, creates libpng.so.2.1.0.4)
makefile.lnx => Linux/ELF makefile (gcc, creates libpng.so.2.1.0.4)
makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc
makefile.mip => MIPS makefile
makefile.aco => Acorn makefile
makefile.ama => Amiga makefile
smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC compiler
(Requires SCOPTIONS, copied from scripts/SCOPTIONS.ppc)
makefile.atr => Atari makefile
makefile.beo => BEOS makefile for X86
makefile.bor => Borland makefile
build.bat => MS-DOS batch file for Borland compiler
makefile.dj2 => DJGPP 2 makefile
@ -65,6 +68,7 @@ include
makevms.com => VMS build script
pngdll.mak => To make a png32bd.dll with Borland C++ 4.5
pngdef.pas => Defines for a png32bd.dll with Borland C++ 4.5
SCOPTIONS.ppc => Used with smakefile.ppc
Copy the file (or files) that you need from the
scripts directory into this directory, for example

14
KNOWNBUG
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@ -1,5 +1,5 @@
Known bugs and suggested enhancements in libpng-1.0.3
Known bugs and suggested enhancements in libpng-1.0.4
1. March 15, 1998 -- OPTIMIZATION -- Kevin Bracey
@ -14,12 +14,12 @@ Known bugs and suggested enhancements in libpng-1.0.3
Question whether i-- or --i is better.
STATUS: Under investigation, postponed until after
libpng-1.0.3. About 160 loops will be turned around
libpng-1.0.4. About 160 loops will be turned around
in libpng-1.0.Nn, for testing.
2. July 4, 1998 -- ENHANCEMENT -- Glenn R-P
libpng-1.0.2 and earlier transform colors to gamma=1.0 space for
libpng-1.0.4 and earlier transform colors to gamma=1.0 space for
merging with background, and then back to the image's gamma. The
bit_depth of the intermediate (gamma=1.0) representation is probably
not sufficient. In the typical gamma=1/2.2 situation, the linear
@ -29,4 +29,12 @@ Known bugs and suggested enhancements in libpng-1.0.3
STATUS: under development.
3. September 1999 -- ENHANCEMENT --
It should be possible to use libpng without floating-point aritmetic.
STATUS: Under investigation, implementation postponed until after
libpng-1.0.4. The application interface will change because replacements
for the png_set_gAMA(), png_set_cHRM(), and corresponding png_get_()
functions will be needed.

72
README
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@ -1,4 +1,4 @@
README for libpng 1.0.3 - January 14, 1999 (shared library 2.1)
README for libpng 1.0.4 - September 17, 1999 (shared library 2.1)
See the note about version numbers near the top of png.h
See INSTALL for instructions on how to install libpng.
@ -49,7 +49,7 @@ 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>
on the PNG implementation mailing list <png-implement@ccrc.wustl.edu>
and not on material submitted to Guy.
For a detailed description on using libpng, read libpng.txt. For
@ -98,8 +98,8 @@ 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 group.
randeg@alumni.rpi.edu
png-implement@dworkin.wustl.edu
randeg@alum.rpi.edu
png-implement@ccrc.wustl.edu
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
@ -108,7 +108,7 @@ addressed to the png-implement list, however.
Please do not send general questions about PNG. Send them to
the address in the specification (png-group@w3.org). At the same
time, please do not send libpng questions to that address, send them to me
or to png-implement@dworkin.wustl.edu. I'll
or to png-implement@ccrc.wustl.edu. 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,
@ -126,8 +126,6 @@ Files in this distribution:
CHANGES => Description of changes between libpng versions
README => This file
TODO => Things not implemented in the current library
ansi2knr.1 => Manual page for ansi2knr
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
@ -155,38 +153,42 @@ Files in this distribution:
pngwtran.c => Write data transformations
pngwutil.c => Write utility functions
scripts => Directory containing scripts for building libpng:
descrip.mms => VMS makefile for MMS or MMK
makefile.std => Generic UNIX makefile
makefile.knr => Archaic UNIX Makefile that converts files with ansi2knr
makefile.dec => DEC Alpha UNIX makefile
makefile.hux => HPUX (10.20 and 11.00) makefile
makefile.sgi => Silicon Graphics IRIX makefile
makefile.sun => Sun makefile
makefile.s2x => Solaris 2.X makefile (gcc, creates libpng.so.2.1.0)
makefile.lnx => Linux/ELF makefile (gcc, creates libpng.so.2.1.0)
makefile.mip => MIPS makefile
makefile.aco => Acorn makefile
makefile.ama => Amiga makefile
smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC compiler
(Requires SCOPTIONS, copied from scripts/SCOPTIONS.ppc)
makefile.atr => Atari makefile
makefile.bor => Borland makefile
build.bat => MS-DOS batch file for Borland compiler
makefile.dj2 => DJGPP 2 makefile
makefile.msc => Microsoft C makefile
makefile.w32 => makefile for Microsoft Visual C++ 4.0 and later
makefile.tc3 => Turbo C 3.0 makefile
makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def)
makefile.wat => Watcom 10a+ Makefile, 32-bit flat memory model
pngos2.def => OS/2 module definition file used by makefile.os2
makevms.com => VMS build script
pngdll.mak => To make a png32bd.dll with Borland C++ 4.5
pngdef.pas => Defines for a png32bd.dll with Borland C++ 4.5
descrip.mms => VMS makefile for MMS or MMK
makefile.std => Generic UNIX makefile
makefile.knr => Archaic UNIX Makefile that converts files with ansi2knr
(Requires ansi2knr.c from ftp://ftp.cs.wisc.edu/ghost)
makefile.dec => DEC Alpha UNIX makefile
makefile.hux => HPUX (10.20 and 11.00) makefile
makefile.sgi => Silicon Graphics IRIX makefile
makefile.sun => Sun makefile
makefile.s2x => Solaris 2.X makefile (gcc, creates libpng.so.2.1.0)
makefile.lnx => Linux/ELF makefile (gcc, creates libpng.so.2.1.0)
makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc
makefile.mip => MIPS makefile
makefile.aco => Acorn makefile
makefile.ama => Amiga makefile
smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC compiler
(Requires SCOPTIONS, copied from scripts/SCOPTIONS.ppc)
makefile.atr => Atari makefile
makefile.beo => BEOS makefile for X86
makefile.bor => Borland makefile
build.bat => MS-DOS batch file for Borland compiler
makefile.dj2 => DJGPP 2 makefile
makefile.msc => Microsoft C makefile
makefile.w32 => makefile for Microsoft Visual C++ 4.0 and later
makefile.tc3 => Turbo C 3.0 makefile
makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def)
pngos2.def => OS/2 module definition file used by makefile.os2
makefile.wat => Watcom 10a+ Makefile, 32-bit flat memory model
makevms.com => VMS build script
pngdll.mak => To make a png32bd.dll with Borland C++ 4.5
pngdef.pas => Defines for a png32bd.dll with Borland C++ 4.5
SCOPTIONS.ppc => Used with smakefile.ppc
Good luck, and happy coding.
-Glenn Randers-Pehrson
Internet: randeg@alumni.rpi.edu
Internet: randeg@alum.rpi.edu
Web: http://www.rpi.edu/~randeg/index.html
-Andreas Eric Dilger

2
TODO
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@ -10,7 +10,6 @@ Support for application-defined chunk handlers.
Improve setjmp/longjmp usage or remove it in favor of returning error codes.
High-level API for reading images.
Add "grayscale->palette" transformation and "palette->grayscale" detection.
Color to gray transformation.
Improved dithering.
Multi-lingual error and warning message support.
Complete sRGB transformation (presently it simply uses gamma=0.45455).
@ -22,3 +21,4 @@ Optional palette (sPLT) creation.
Histogram creation.
Text conversion between different code pages (Latin-1 -> Mac and DOS).
Improve API by hiding the info_ptr.
Make a no-floating-point version.

19
Y2KINFO
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@ -6,9 +6,9 @@
Since the PNG Development group is an ad-hoc body, we can't make
an official declaration.
This is your unofficial assurance that libpng from version 0.81 and
upward are Y2K compliant. It is my belief that earlier versions were
also Y2K compliant.
This is your unofficial assurance that libpng from version 0.71 and
upward through 1.0.4 are Y2K compliant. It is my belief that earlier
versions were also Y2K compliant.
Libpng only has three year fields. One is a 2-byte unsigned integer
that will hold years up to 65535. The other two hold the date in text
@ -37,14 +37,17 @@
clock time, which returns (year - 1900), which we properly convert to
the full 4-digit year. There is a possibility that applications using
libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
function, or incorrectly passing only a 2-digit year instead of
"year - 1900" into the png_convert_from_struct_tm() function, but this
is not under our control. The libpng documentation has always stated
that it works with 4-digit years, and the APIs have been documented as
such.
function, or that they are incorrectly passing only a 2-digit year
instead of "year - 1900" into the png_convert_from_struct_tm() function,
but this is not under our control. The libpng documentation has always
stated that it works with 4-digit years, and the APIs have been
documented as such.
The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
integer to hold the year, and can hold years as large as 65535.
zlib, upon which libpng depends, is also Y2K compliant. It contains
no date-related code.
Glenn Randers-Pehrson

36
ansi2knr.1
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@ -1,36 +0,0 @@
.TH ANSI2KNR 1 "19 Jan 1996"
.SH NAME
ansi2knr \- convert ANSI C to Kernighan & Ritchie C
.SH SYNOPSIS
.I ansi2knr
[--varargs] input_file [output_file]
.SH DESCRIPTION
If no output_file is supplied, output goes to stdout.
.br
There are no error messages.
.sp
.I ansi2knr
recognizes function definitions by seeing a non-keyword identifier at the left
margin, followed by a left parenthesis, with a right parenthesis as the last
character on the line, and with a left brace as the first token on the
following line (ignoring possible intervening comments). It will recognize a
multi-line header provided that no intervening line ends with a left or right
brace or a semicolon. These algorithms ignore whitespace and comments, except
that the function name must be the first thing on the line.
.sp
The following constructs will confuse it:
.br
- Any other construct that starts at the left margin and follows the
above syntax (such as a macro or function call).
.br
- Some macros that tinker with the syntax of the function header.
.sp
The --varargs switch is obsolete, and is recognized only for
backwards compatibility. The present version of
.I ansi2knr
will always attempt to convert a ... argument to va_alist and va_dcl.
.SH AUTHOR
L. Peter Deutsch <ghost@aladdin.com> wrote the original ansi2knr and
continues to maintain the current version; most of the code in the current
version is his work. ansi2knr also includes contributions by Francois
Pinard <pinard@iro.umontreal.ca> and Jim Avera <jima@netcom.com>.

695
ansi2knr.c
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@ -1,695 +0,0 @@
/* ansi2knr.c */
/* Convert ANSI C function definitions to K&R ("traditional C") syntax
Copyright (C) 1989 Aladdin Enterprises. All rights reserved.
Copyright (C) 1988 Richard M. Stallman
ansi2knr is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY. No author or distributor accepts responsibility to anyone for the
consequences of using it or for whether it serves any particular purpose or
works at all, unless he says so in writing. Refer to the GNU General Public
License (the "GPL") for full details.
Everyone is granted permission to copy, modify and redistribute ansi2knr,
but only under the conditions described in the GPL. A copy of this license
is supposed to have been given to you along with ansi2knr so you can know
your rights and responsibilities. It should be in a file named COPYLEFT.
[In the LIBPNG distribution, the GPL appears below, not in a separate file.]
Among other things, the copyright notice and this notice must be preserved
on all copies.
We explicitly state here what we believe is already implied by the GPL: if
the ansi2knr program is distributed as a separate source file and a
separate executable file which are aggregated on a storage medium together
with another program, this in itself does not bring the other program under
the GPL, nor does the mere fact that such a program or the procedures for
constructing it invoke the ansi2knr executable bring any other part of the
program under the GPL.
*/
/*
---------- Here is the GNU GPL file COPYLEFT, referred to above ----------
----- These terms do NOT apply to the LIBPNG software itself; see README ------
GHOSTSCRIPT GENERAL PUBLIC LICENSE
(Clarified 11 Feb 1988)
Copyright (C) 1988 Richard M. Stallman
Everyone is permitted to copy and distribute verbatim copies of this
license, but changing it is not allowed. You can also use this wording
to make the terms for other programs.
The license agreements of most software companies keep you at the
mercy of those companies. By contrast, our general public license is
intended to give everyone the right to share Ghostscript. To make sure
that you get the rights we want you to have, we need to make
restrictions that forbid anyone to deny you these rights or to ask you
to surrender the rights. Hence this license agreement.
Specifically, we want to make sure that you have the right to give
away copies of Ghostscript, that you receive source code or else can get
it if you want it, that you can change Ghostscript or use pieces of it
in new free programs, and that you know you can do these things.
To make sure that everyone has such rights, we have to forbid you to
deprive anyone else of these rights. For example, if you distribute
copies of Ghostscript, you must give the recipients all the rights that
you have. You must make sure that they, too, receive or can get the
source code. And you must tell them their rights.
Also, for our own protection, we must make certain that everyone finds
out that there is no warranty for Ghostscript. If Ghostscript is
modified by someone else and passed on, we want its recipients to know
that what they have is not what we distributed, so that any problems
introduced by others will not reflect on our reputation.
Therefore we (Richard M. Stallman and the Free Software Foundation,
Inc.) make the following terms which say what you must do to be allowed
to distribute or change Ghostscript.
COPYING POLICIES
1. You may copy and distribute verbatim copies of Ghostscript source
code as you receive it, in any medium, provided that you conspicuously
and appropriately publish on each copy a valid copyright and license
notice "Copyright (C) 1989 Aladdin Enterprises. All rights reserved.
Distributed by Free Software Foundation, Inc." (or with whatever year is
appropriate); keep intact the notices on all files that refer to this
License Agreement and to the absence of any warranty; and give any other
recipients of the Ghostscript program a copy of this License Agreement
along with the program. You may charge a distribution fee for the
physical act of transferring a copy.
2. You may modify your copy or copies of Ghostscript or any portion of
it, and copy and distribute such modifications under the terms of
Paragraph 1 above, provided that you also do the following:
a) cause the modified files to carry prominent notices stating
that you changed the files and the date of any change; and
b) cause the whole of any work that you distribute or publish,
that in whole or in part contains or is a derivative of Ghostscript
or any part thereof, to be licensed at no charge to all third
parties on terms identical to those contained in this License
Agreement (except that you may choose to grant more extensive
warranty protection to some or all third parties, at your option).
c) You may charge a distribution fee for the physical act of
transferring a copy, and you may at your option offer warranty
protection in exchange for a fee.
Mere aggregation of another unrelated program with this program (or its
derivative) on a volume of a storage or distribution medium does not bring
the other program under the scope of these terms.
3. You may copy and distribute Ghostscript (or a portion or derivative
of it, under Paragraph 2) in object code or executable form under the
terms of Paragraphs 1 and 2 above provided that you also do one of the
following:
a) accompany it with the complete corresponding machine-readable
source code, which must be distributed under the terms of
Paragraphs 1 and 2 above; or,
b) accompany it with a written offer, valid for at least three
years, to give any third party free (except for a nominal
shipping charge) a complete machine-readable copy of the
corresponding source code, to be distributed under the terms of
Paragraphs 1 and 2 above; or,
c) accompany it with the information you received as to where the
corresponding source code may be obtained. (This alternative is
allowed only for noncommercial distribution and only if you
received the program in object code or executable form alone.)
For an executable file, complete source code means all the source code for
all modules it contains; but, as a special exception, it need not include
source code for modules which are standard libraries that accompany the
operating system on which the executable file runs.
4. You may not copy, sublicense, distribute or transfer Ghostscript
except as expressly provided under this License Agreement. Any attempt
otherwise to copy, sublicense, distribute or transfer Ghostscript is
void and your rights to use the program under this License agreement
shall be automatically terminated. However, parties who have received
computer software programs from you with this License Agreement will not
have their licenses terminated so long as such parties remain in full
compliance.
5. If you wish to incorporate parts of Ghostscript into other free
programs whose distribution conditions are different, write to the Free
Software Foundation at 675 Mass Ave, Cambridge, MA 02139. We have not
yet worked out a simple rule that can be stated here, but we will often
permit this. We will be guided by the two goals of preserving the free
status of all derivatives of our free software and of promoting the
sharing and reuse of software.
Your comments and suggestions about our licensing policies and our
software are welcome! Please contact the Free Software Foundation,
Inc., 675 Mass Ave, Cambridge, MA 02139, or call (617) 876-3296.
NO WARRANTY
BECAUSE GHOSTSCRIPT IS LICENSED FREE OF CHARGE, WE PROVIDE ABSOLUTELY
NO WARRANTY, TO THE EXTENT PERMITTED BY APPLICABLE STATE LAW. EXCEPT
WHEN OTHERWISE STATED IN WRITING, FREE SOFTWARE FOUNDATION, INC, RICHARD
M. STALLMAN, ALADDIN ENTERPRISES, L. PETER DEUTSCH, AND/OR OTHER PARTIES
PROVIDE GHOSTSCRIPT "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF GHOSTSCRIPT IS WITH
YOU. SHOULD GHOSTSCRIPT PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
NECESSARY SERVICING, REPAIR OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW WILL RICHARD M.
STALLMAN, THE FREE SOFTWARE FOUNDATION, INC., L. PETER DEUTSCH, ALADDIN
ENTERPRISES, AND/OR ANY OTHER PARTY WHO MAY MODIFY AND REDISTRIBUTE
GHOSTSCRIPT AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING
ANY LOST PROFITS, LOST MONIES, OR OTHER SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
(INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED
INACCURATE OR LOSSES SUSTAINED BY THIRD PARTIES OR A FAILURE OF THE
PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS) GHOSTSCRIPT, EVEN IF YOU
HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, OR FOR ANY CLAIM
BY ANY OTHER PARTY.
-------------------- End of file COPYLEFT ------------------------------
*/
/*
* Usage:
ansi2knr input_file [output_file]
* If no output_file is supplied, output goes to stdout.
* There are no error messages.
*
* ansi2knr recognizes function definitions by seeing a non-keyword
* identifier at the left margin, followed by a left parenthesis,
* with a right parenthesis as the last character on the line,
* and with a left brace as the first token on the following line
* (ignoring possible intervening comments).
* It will recognize a multi-line header provided that no intervening
* line ends with a left or right brace or a semicolon.
* These algorithms ignore whitespace and comments, except that
* the function name must be the first thing on the line.
* The following constructs will confuse it:
* - Any other construct that starts at the left margin and
* follows the above syntax (such as a macro or function call).
* - Some macros that tinker with the syntax of the function header.
*/
/*
* The original and principal author of ansi2knr is L. Peter Deutsch
* <ghost@aladdin.com>. Other authors are noted in the change history
* that follows (in reverse chronological order):
lpd 96-01-21 added code to cope with not HAVE_CONFIG_H and with
compilers that don't understand void, as suggested by
Tom Lane
lpd 96-01-15 changed to require that the first non-comment token
on the line following a function header be a left brace,
to reduce sensitivity to macros, as suggested by Tom Lane
<tgl@sss.pgh.pa.us>
lpd 95-06-22 removed #ifndefs whose sole purpose was to define
undefined preprocessor symbols as 0; changed all #ifdefs
for configuration symbols to #ifs
lpd 95-04-05 changed copyright notice to make it clear that
including ansi2knr in a program does not bring the entire
program under the GPL
lpd 94-12-18 added conditionals for systems where ctype macros
don't handle 8-bit characters properly, suggested by
Francois Pinard <pinard@iro.umontreal.ca>;
removed --varargs switch (this is now the default)
lpd 94-10-10 removed CONFIG_BROKETS conditional
lpd 94-07-16 added some conditionals to help GNU `configure',
suggested by Francois Pinard <pinard@iro.umontreal.ca>;
properly erase prototype args in function parameters,
contributed by Jim Avera <jima@netcom.com>;
correct error in writeblanks (it shouldn't erase EOLs)
lpd 89-xx-xx original version
*/
/* Most of the conditionals here are to make ansi2knr work with */
/* or without the GNU configure machinery. */
#if HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdio.h>
#include <ctype.h>
#if HAVE_CONFIG_H
/*
For properly autoconfiguring ansi2knr, use AC_CONFIG_HEADER(config.h).
This will define HAVE_CONFIG_H and so, activate the following lines.
*/
# if STDC_HEADERS || HAVE_STRING_H
# include <string.h>
# else
# include <strings.h>
# endif
#else /* not HAVE_CONFIG_H */
/* Otherwise do it the hard way */
# ifdef BSD
# include <strings.h>
# else
# ifdef VMS
extern int strlen(), strncmp();
# else
# include <string.h>
# endif
# endif
#endif /* not HAVE_CONFIG_H */
#if STDC_HEADERS
# include <stdlib.h>
#else
/*
malloc and free should be declared in stdlib.h,
but if you've got a K&R compiler, they probably aren't.
*/
# ifdef MSDOS
# include <malloc.h>
# else
# ifdef VMS
extern char *malloc();
extern void free();
# else
extern char *malloc();
extern int free();
# endif
# endif
#endif
/*
* The ctype macros don't always handle 8-bit characters correctly.
* Compensate for this here.
*/
#ifdef isascii
# undef HAVE_ISASCII /* just in case */
# define HAVE_ISASCII 1
#else
#endif
#if STDC_HEADERS || !HAVE_ISASCII
# define is_ascii(c) 1
#else
# define is_ascii(c) isascii(c)
#endif
#define is_space(c) (is_ascii(c) && isspace(c))
#define is_alpha(c) (is_ascii(c) && isalpha(c))
#define is_alnum(c) (is_ascii(c) && isalnum(c))
/* Scanning macros */
#define isidchar(ch) (is_alnum(ch) || (ch) == '_')
#define isidfirstchar(ch) (is_alpha(ch) || (ch) == '_')
/* Forward references */
char *skipspace();
int writeblanks();
int test1();
int convert1();
/* The main program */
int
main(argc, argv)
int argc;
char *argv[];
{ FILE *in, *out;
#define bufsize 5000 /* arbitrary size */
char *buf;
char *line;
char *more;
/*
* In previous versions, ansi2knr recognized a --varargs switch.
* If this switch was supplied, ansi2knr would attempt to convert
* a ... argument to va_alist and va_dcl; if this switch was not
* supplied, ansi2knr would simply drop any such arguments.
* Now, ansi2knr always does this conversion, and we only
* check for this switch for backward compatibility.
*/
int convert_varargs = 1;
if ( argc > 1 && argv[1][0] == '-' )
{ if ( !strcmp(argv[1], "--varargs") )
{ convert_varargs = 1;
argc--;
argv++;
}
else
{ fprintf(stderr, "Unrecognized switch: %s\n", argv[1]);
exit(1);
}
}
switch ( argc )
{
default:
printf("Usage: ansi2knr input_file [output_file]\n");
exit(0);
case 2:
out = stdout;
break;
case 3:
out = fopen(argv[2], "w");
if ( out == NULL )
{ fprintf(stderr, "Cannot open output file %s\n", argv[2]);
exit(1);
}
}
in = fopen(argv[1], "r");
if ( in == NULL )
{ fprintf(stderr, "Cannot open input file %s\n", argv[1]);
exit(1);
}
fprintf(out, "#line 1 \"%s\"\n", argv[1]);
buf = malloc(bufsize);
line = buf;
while ( fgets(line, (unsigned)(buf + bufsize - line), in) != NULL )
{
test: line += strlen(line);
switch ( test1(buf) )
{
case 2: /* a function header */
convert1(buf, out, 1, convert_varargs);
break;
case 1: /* a function */
/* Check for a { at the start of the next line. */
more = ++line;
f: if ( line >= buf + (bufsize - 1) ) /* overflow check */
goto wl;
if ( fgets(line, (unsigned)(buf + bufsize - line), in) == NULL )
goto wl;
switch ( *skipspace(more, 1) )
{
case '{':
/* Definitely a function header. */
convert1(buf, out, 0, convert_varargs);
fputs(more, out);
break;
case 0:
/* The next line was blank or a comment: */
/* keep scanning for a non-comment. */
line += strlen(line);
goto f;
default:
/* buf isn't a function header, but */
/* more might be. */
fputs(buf, out);
strcpy(buf, more);
line = buf;
goto test;
}
break;
case -1: /* maybe the start of a function */
if ( line != buf + (bufsize - 1) ) /* overflow check */
continue;
/* falls through */
default: /* not a function */
wl: fputs(buf, out);
break;
}
line = buf;
}
if ( line != buf )
fputs(buf, out);
free(buf);
fclose(out);
fclose(in);
return 0;
}
/* Skip over space and comments, in either direction. */
char *
skipspace(p, dir)
register char *p;
register int dir; /* 1 for forward, -1 for backward */
{ for ( ; ; )
{ while ( is_space(*p) )
p += dir;
if ( !(*p == '/' && p[dir] == '*') )
break;
p += dir; p += dir;
while ( !(*p == '*' && p[dir] == '/') )
{ if ( *p == 0 )
return p; /* multi-line comment?? */
p += dir;
}
p += dir; p += dir;
}
return p;
}
/*
* Write blanks over part of a string.
* Don't overwrite end-of-line characters.
*/
int
writeblanks(start, end)
char *start;
char *end;
{ char *p;
for ( p = start; p < end; p++ )
if ( *p != '\r' && *p != '\n' )
*p = ' ';
return 0;
}
/*
* Test whether the string in buf is a function definition.
* The string may contain and/or end with a newline.
* Return as follows:
* 0 - definitely not a function definition;
* 1 - definitely a function definition;
* 2 - definitely a function prototype (NOT USED);
* -1 - may be the beginning of a function definition,
* append another line and look again.
* The reason we don't attempt to convert function prototypes is that
* Ghostscript's declaration-generating macros look too much like
* prototypes, and confuse the algorithms.
*/
int
test1(buf)
char *buf;
{ register char *p = buf;
char *bend;
char *endfn;
int contin;
if ( !isidfirstchar(*p) )
return 0; /* no name at left margin */
bend = skipspace(buf + strlen(buf) - 1, -1);
switch ( *bend )
{
case ';': contin = 0 /*2*/; break;
case ')': contin = 1; break;
case '{': return 0; /* not a function */
case '}': return 0; /* not a function */
default: contin = -1;
}
while ( isidchar(*p) )
p++;
endfn = p;
p = skipspace(p, 1);
if ( *p++ != '(' )
return 0; /* not a function */
p = skipspace(p, 1);
if ( *p == ')' )
return 0; /* no parameters */
/* Check that the apparent function name isn't a keyword. */
/* We only need to check for keywords that could be followed */
/* by a left parenthesis (which, unfortunately, is most of them). */
{ static char *words[] =
{ "asm", "auto", "case", "char", "const", "double",
"extern", "float", "for", "if", "int", "long",
"register", "return", "short", "signed", "sizeof",
"static", "switch", "typedef", "unsigned",
"void", "volatile", "while", 0
};
char **key = words;
char *kp;
int len = endfn - buf;
while ( (kp = *key) != 0 )
{ if ( strlen(kp) == len && !strncmp(kp, buf, len) )
return 0; /* name is a keyword */
key++;
}
}
return contin;
}
/* Convert a recognized function definition or header to K&R syntax. */
int
convert1(buf, out, header, convert_varargs)
char *buf;
FILE *out;
int header; /* Boolean */
int convert_varargs; /* Boolean */
{ char *endfn;
register char *p;
char **breaks;
unsigned num_breaks = 2; /* for testing */
char **btop;
char **bp;
char **ap;
char *vararg = 0;
/* Pre-ANSI implementations don't agree on whether strchr */
/* is called strchr or index, so we open-code it here. */
for ( endfn = buf; *(endfn++) != '('; )
;
top: p = endfn;
breaks = (char **)malloc(sizeof(char *) * num_breaks * 2);
if ( breaks == 0 )
{ /* Couldn't allocate break table, give up */
fprintf(stderr, "Unable to allocate break table!\n");
fputs(buf, out);
return -1;
}
btop = breaks + num_breaks * 2 - 2;
bp = breaks;
/* Parse the argument list */
do
{ int level = 0;
char *lp = NULL;
char *rp;
char *end = NULL;
if ( bp >= btop )
{ /* Filled up break table. */
/* Allocate a bigger one and start over. */
free((char *)breaks);
num_breaks <<= 1;
goto top;
}
*bp++ = p;
/* Find the end of the argument */
for ( ; end == NULL; p++ )
{ switch(*p)
{
case ',':
if ( !level ) end = p;
break;
case '(':
if ( !level ) lp = p;
level++;
break;
case ')':
if ( --level < 0 ) end = p;
else rp = p;
break;
case '/':
p = skipspace(p, 1) - 1;
break;
default:
;
}
}
/* Erase any embedded prototype parameters. */
if ( lp )
writeblanks(lp + 1, rp);
p--; /* back up over terminator */
/* Find the name being declared. */
/* This is complicated because of procedure and */
/* array modifiers. */
for ( ; ; )
{ p = skipspace(p - 1, -1);
switch ( *p )
{
case ']': /* skip array dimension(s) */
case ')': /* skip procedure args OR name */
{ int level = 1;
while ( level )
switch ( *--p )
{
case ']': case ')': level++; break;
case '[': case '(': level--; break;
case '/': p = skipspace(p, -1) + 1; break;
default: ;
}
}
if ( *p == '(' && *skipspace(p + 1, 1) == '*' )
{ /* We found the name being declared */
while ( !isidfirstchar(*p) )
p = skipspace(p, 1) + 1;
goto found;
}
break;
default:
goto found;
}
}
found: if ( *p == '.' && p[-1] == '.' && p[-2] == '.' )
{ if ( convert_varargs )
{ *bp++ = "va_alist";
vararg = p-2;
}
else
{ p++;
if ( bp == breaks + 1 ) /* sole argument */
writeblanks(breaks[0], p);
else
writeblanks(bp[-1] - 1, p);
bp--;
}
}
else
{ while ( isidchar(*p) ) p--;
*bp++ = p+1;
}
p = end;
}
while ( *p++ == ',' );
*bp = p;
/* Make a special check for 'void' arglist */
if ( bp == breaks+2 )
{ p = skipspace(breaks[0], 1);
if ( !strncmp(p, "void", 4) )
{ p = skipspace(p+4, 1);
if ( p == breaks[2] - 1 )
{ bp = breaks; /* yup, pretend arglist is empty */
writeblanks(breaks[0], p + 1);
}
}
}
/* Put out the function name and left parenthesis. */
p = buf;
while ( p != endfn ) putc(*p, out), p++;
/* Put out the declaration. */
if ( header )
{ fputs(");", out);
for ( p = breaks[0]; *p; p++ )
if ( *p == '\r' || *p == '\n' )
putc(*p, out);
}
else
{ for ( ap = breaks+1; ap < bp; ap += 2 )
{ p = *ap;
while ( isidchar(*p) )
putc(*p, out), p++;
if ( ap < bp - 1 )
fputs(", ", out);
}
fputs(") ", out);
/* Put out the argument declarations */
for ( ap = breaks+2; ap <= bp; ap += 2 )
(*ap)[-1] = ';';
if ( vararg != 0 )
{ *vararg = 0;
fputs(breaks[0], out); /* any prior args */
fputs("va_dcl", out); /* the final arg */
fputs(bp[0], out);
}
else
fputs(breaks[0], out);
}
free((char *)breaks);
return 0;
}

2
example.c
View File

@ -151,7 +151,7 @@ void read_png(FILE *fp, unsigned int sig_read) /* file is already open */
/* tell libpng to strip 16 bit/color files down to 8 bits/color */
png_set_strip_16(png_ptr);
/* Strip alpha bytes from the input data without combining with th
/* Strip alpha bytes from the input data without combining with the
* background (not recommended).
*/
png_set_strip_alpha(png_ptr);

849
libpng.3
View File

File diff suppressed because it is too large Load Diff

101
libpng.txt
View File

@ -1,8 +1,8 @@
libpng.txt - A description on how to use and modify libpng
libpng version 1.0.3 - January 14, 1999
libpng version 1.0.4 - September 17, 1999
Updated and distributed by Glenn Randers-Pehrson
<randeg@alumni.rpi.edu>
<randeg@alum.rpi.edu>
Copyright (c) 1998, 1999 Glenn Randers-Pehrson
For conditions of distribution and use, see copyright
notice in png.h.
@ -22,6 +22,7 @@ libpng.txt - A description on how to use and modify libpng
Copyright (c) 1995 Frank J. T. Wojcik
December 18, 1995 && January 20, 1996
*
I. Introduction
This file describes how to use and modify the PNG reference library
@ -35,11 +36,17 @@ INSTALL file for instructions on how to install libpng.
Libpng was written as a companion to the PNG specification, as a way
of reducing the amount of time and effort it takes to support the PNG
file format in application programs. The PNG specification is available
file format in application programs.
The PNG-1.2 specification is available at <http://www.cdrom.com/png>.
The PNG-1.0 specification is available
as RFC 2083 <ftp://ftp.uu.net/graphics/png/documents/> and as a
W3C Recommendation <http://www.w3.org/TR/REC.png.html>. Some
additional chunks are described in the special-purpose public chunks
documents at <ftp://ftp.uu.net/graphics/png/documents/>. Other information
documents at <ftp://ftp.uu.net/graphics/png/documents/>.
Other information
about PNG, and the latest version of libpng, can be found at the PNG home
page, <http://www.cdrom.com/pub/png/>.
@ -261,6 +268,21 @@ You must supply the function
See pngtest.c for a working example. Your function will be called
after all of the other transformations have been processed.
You can also set up a pointer to a user structure for use by your
callback function, and you can inform libpng that your transform
function will change the number of channels or bit depth with the
function
png_set_user_transform_info(png_ptr, user_ptr,
user_depth, user_channels);
You can retrieve the pointer via the function
png_get_user_transform_ptr(). For example:
voidp read_user_transform_ptr =
png_get_user_transform_ptr(png_ptr);
You are now ready to read all the file information up to the actual
image data. You do this with a call to png_read_info().
@ -506,13 +528,18 @@ grayscale images with bit depths of 2 or 4 or if there is a multiple-image
viewing application that wishes to treat all images in the same way.
if (color_type == PNG_COLOR_TYPE_PALETTE &&
bit_depth <= 8) png_set_expand(png_ptr);
bit_depth <= 8) png_set_palette_to_rgb(png_ptr);
if (color_type == PNG_COLOR_TYPE_GRAY &&
bit_depth < 8) png_set_expand(png_ptr);
bit_depth < 8) png_set_gray_1_2_4_to_8(png_ptr);
if (png_get_valid(png_ptr, info_ptr,
PNG_INFO_tRNS)) png_set_expand(png_ptr);
PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
These three functions are actually aliases for png_set_expand(), added
in libpng version 1.0.4, with the function names expanded to improve code
readability. In some future version they may actually do different
things.
PNG can have files with 16 bits per channel. If you only can handle
8 bits per channel, this will strip the pixels down to 8 bit.
@ -599,7 +626,7 @@ and blue channels, leaving the green channel in the gray position.
if (color_type == PNG_COLOR_TYPE_RGB ||
color_type == PNG_COLOR_TYPE_RGB_ALPHA)
png_set_rgb_to_gray(png_ptr, error_action,
float red_weight, float green_weight);
double red_weight, double green_weight);
error_action = 1: silently do the conversion
error_action = 2: issue a warning if the original
@ -648,7 +675,8 @@ which can be expressed with integers as
The calculation is done in a linear colorspace, if the image gamma
is known.
If you have a grayscale and you are using png_set_expand() to change to
If you have a grayscale and you are using png_set_expand_depth() or
png_set_expand() to change to
a higher bit-depth, you must either supply the background color as a gray
value at the original file bit-depth (need_expand = 1) or else supply the
background color as an RGB triplet at the final, expanded bit depth
@ -681,6 +709,8 @@ the amount of additional gamma correction needed to compensate for
a (viewing_gamma=1.25) environment. In a dim or brightly lit room, no
compensation other than the display_gamma is needed (viewing_gamma=1.0).
double gamma, screen_gamma;
if (/* We have a user-defined screen
gamma value */)
{
@ -691,7 +721,7 @@ compensation other than the display_gamma is needed (viewing_gamma=1.0).
else if ((gamma_str = getenv("SCREEN_GAMMA"))
!= NULL)
{
screen_gamma = atof(gamma_str);
screen_gamma = (double)atof(gamma_str);
}
/* If we don't have another value */
else
@ -831,7 +861,7 @@ row_pointers:
png_read_row(png_ptr, &row_pointers, NULL);
If the file is interlaced (info_ptr->interlace_type != 0), things get
somewhat harder. The only current (PNG Specification version 1.0)
somewhat harder. The only current (PNG Specification version 1.2)
interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7)
is a somewhat complicated 2D interlace scheme, known as Adam7, that
breaks down an image into seven smaller images of varying size, based
@ -1194,7 +1224,7 @@ have no special needs in this area, let the library do what it wants by
not calling this function at all, as it has been tuned to deliver a good
speed/compression ratio. The second parameter to png_set_filter() is
the filter method, for which the only valid value is '0' (as of the
October 1996 PNG specification, version 1.0). The third parameter is a
July 1999 PNG specification, version 1.2). The third parameter is a
flag that indicates which filter type(s) are to be tested for each
scanline. See the Compression Library for details on the specific filter
types.
@ -1226,7 +1256,7 @@ data. See the Compression Library for details on the compression levels.
You now need to fill in the png_info structure with all the data you
wish to write before the actual image. Note that the only thing you
are allowed to write after the image is the text chunks and the time
chunk (as of PNG Specification 1.0, anyway). See png_write_end() and
chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
the latest PNG specification for more information on that. If you
wish to write them before the image, fill them in now, and flag that
data as being valid. If you want to wait until after the data, don't
@ -1555,7 +1585,21 @@ You must supply the function
row_info, png_bytep data)
See pngtest.c for a working example. Your function will be called
before any of the other transformations have been processed.
before any of the other transformations are processed.
You can also set up a pointer to a user structure for use by your
callback function.
png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
The user_channels and user_depth parameters of this function are ignored
when writing; you can set them to zero as shown.
You can retrieve the pointer via the function
png_get_user_transform_ptr(). For example:
voidp write_user_transform_ptr =
png_get_user_transform_ptr(png_ptr);
It is possible to have libpng flush any pending output, either manually,
or automatically after a certain number of lines have been written. To
@ -1612,8 +1656,8 @@ row_pointers:
png_write_row(png_ptr, &row_pointer);
When the file is interlaced, things can get a good deal more
complicated. The only currently (as of February 1998 -- PNG Specification
version 1.0, dated October 1996) defined interlacing scheme for PNG files
complicated. The only currently (as of August 1999 -- PNG Specification
version 1.2, dated July 1999) defined interlacing scheme for PNG files
is the "Adam7" interlace scheme, that breaks down an
image into seven smaller images of varying size. libpng will build
these images for you, or you can do them yourself. If you want to
@ -1658,7 +1702,6 @@ palette, or histogram, before the call to png_destroy_write_struct();
For a more compact example of writing a PNG image, see the file example.c.
V. Modifying/Customizing libpng:
There are two issues here. The first is changing how libpng does
@ -1685,7 +1728,8 @@ which currently just call fread() and fwrite(). The FILE * is stored in
png_struct and is initialized via png_init_io(). If you wish to change
the method of I/O, the library supplies callbacks that you can set
through the function png_set_read_fn() and png_set_write_fn() at run
time, instead of calling the png_init_io() function. These functions
time, instead of calling the png_init_io() function.
These functions
also provide a void pointer that can be retrieved via the function
png_get_io_ptr(). For example:
@ -1852,7 +1896,7 @@ images (with and without alpha), but not for paletted images nor
for any images with bit depths less than 8 bits/pixel.
The 'method' parameter sets the main filtering method, which is
currently only '0' in the PNG 1.0 specification. The 'filters'
currently only '0' in the PNG 1.2 specification. The 'filters'
parameter sets which filter(s), if any, should be used for each
scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
to turn filtering on and off, respectively.
@ -2021,9 +2065,9 @@ January 13, 1999
Since the PNG Development group is an ad-hoc body, we can't make
an official declaration.
This is your unofficial assurance that libpng from version 0.81 and
upward are Y2K compliant. It is my belief that earlier versions were
also Y2K compliant.
This is your unofficial assurance that libpng from version 0.71 and
upward through 1.0.4 are Y2K compliant. It is my belief that earlier
versions were also Y2K compliant.
Libpng only has three year fields. One is a 2-byte unsigned integer that
will hold years up to 65535. The other two hold the date in text
@ -2052,15 +2096,18 @@ png_convert_from_time_t() function calls gmtime() to convert from system
clock time, which returns (year - 1900), which we properly convert to
the full 4-digit year. There is a possibility that applications using
libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
function, or incorrectly passing only a 2-digit year instead of
"year - 1900" into the png_convert_from_struct_tm() function, but this
is not under our control. The libpng documentation has always stated
that it works with 4-digit years, and the APIs have been documented as
such.
function, or that they are incorrectly passing only a 2-digit year
instead of "year - 1900" into the png_convert_from_struct_tm() function,
but this is not under our control. The libpng documentation has always
stated that it works with 4-digit years, and the APIs have been
documented as such.
The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
integer to hold the year, and can hold years as large as 65535.
zlib, upon which libpng depends, is also Y2K compliant. It contains
no date-related code.
Glenn Randers-Pehrson
libpng maintainer

580
libpngpf.3
View File

@ -3,337 +3,495 @@
libpng \- Portable Network Graphics (PNG) Reference Library 1.0.3 - January 14, 1999
(private functions)