Imported from libpng-1.0.2a.tar
This commit is contained in:
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89
ANNOUNCE
89
ANNOUNCE
@ -1,67 +1,38 @@
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Libpng 1.0.2 - June 14, 1998
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Libpng 1.0.2a - December 29, 1998
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This is a public release of libpng, intended for use in production codes.
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This is not intended to be a public release. It will be replaced
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within a few weeks by a public version or by another test version.
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Changes since the previous public release (1.0.1):
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Changes since the last public release:
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Optimized Paeth calculations by replacing abs() function calls with intrinsics
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plus other loop optimizations. Improves avg decoding speed by about 20%.
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Commented out i386istic "align" compiler flags in makefile.lnx.
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Reduced the default warning level in some makefiles, to make them consistent.
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Removed references to IJG and JPEG in the ansi2knr.c copyright statement.
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Fixed a bug in png_do_strip_filler with XXRRGGBB => RRGGBB transformation.
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Added grayscale and 16-bit capability to png_do_read_filler().
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Fixed a bug in pngset.c, introduced in version 0.99c, that sets rowbytes
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too large when writing an image with bit_depth < 8 (Bob Dellaca).
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Corrected some bugs in the experimental weighted filtering heuristics.
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Moved a misplaced pngrutil code block that truncates tRNS if it has more
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than num_palette entries -- test was done before num_palette was defined.
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Fixed a png_convert_to_rfc1123() bug that converts day 31 to 0 (Steve Eddins).
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Changed compiler flags in makefile.wat for better optimization (Pawel Mrochen).
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Relocated png_do_gray_to_rgb() within png_do_read_transformations() (Greg).
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Relocated the png_composite macros from pngrtran.c to png.h (Greg).
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Added makefile.sco (contributed by Mike Hopkirk).
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Fixed a bug in pngrtran.c that would set channels=5 under some circumstances.
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Added warnings when people try to use transforms they've defined out.
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Collapsed 4 "i" and "c" loops into single "i" loops in pngrtran and pngwtran.
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Revised paragraph about png_set_expand() in libpng.txt and libpng.3 (Greg)
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Added max_pixel_depth=32 in pngrutil.c when using FILLER with palette images.
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Moved PNG_WRITE_WEIGHTED_FILTER_SUPPORTED and PNG_WRITE_FLUSH_SUPPORTED
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out of the PNG_WRITE_TRANSFORMS_NOT_SUPPORTED block of pngconf.h
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Added "PNG_NO_WRITE_TRANSFORMS" etc., as alternatives for *_NOT_SUPPORTED,
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for consistency, in pngconf.h
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Added individual "ifndef PNG_NO_CAPABILITY" for the capabilities in pngconf.h
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to make it easier to remove unwanted capabilities via the compile line
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Made some corrections to grammar (which, it's) in documentation (Greg).
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Corrected example.c, use of row_pointers in png_write_image().
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Revised png_read_rows() to avoid repeated if-testing for NULL (A Kleinert)
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More corrections to example.c, use of row_pointers in png_write_image()
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and png_read_rows().
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Added pngdll.mak and pngdef.pas to scripts directory, contributed by
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Bob Dellaca, to make a png32bd.dll with Borland C++ 4.5
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Fixed error in example.c with png_set_text: num_text is 3, not 2 (Guido V.)
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Changed several loops from count-down to count-up, for consistency.
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Revised libpng.txt and libpng.3 description of png_set_read|write_fn(), and
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added warnings when people try to set png_read_fn and png_write_fn in
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the same structure.
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Added a test such that png_do_gamma will be done when num_trans==0
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for truecolor images that have defined a background. This corrects an
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error that was introduced in libpng-0.90 that can cause gamma processing
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to be skipped.
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Added tests in png.h to include "trans" and "trans_values" in structures
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when PNG_READ_BACKGROUND_SUPPORTED or PNG_READ_EXPAND_SUPPORTED is defined.
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Add png_free(png_ptr->time_buffer) in png_destroy_read_struct()
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Moved png_convert_to_rfc_1123() from pngwrite.c to png.c
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Added capability for user-provided malloc_fn() and free_fn() functions,
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and revised pngtest.c to demonstrate their use, replacing the
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PNGTEST_DEBUG_MEM feature.
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Added makefile.w32, for Microsoft C++ 4.0 and later (Tim Wegner).
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Fixed two bugs in makefile.bor
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libpng-1.0.2a:
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Replaced and extended code that was removed from png_set_filler() in 1.0.1a.
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Fixed a bug in png_do_filler() that made it fail to write filler bytes in
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the left-most pixel of each row (Kevin Bracey).
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Changed "static pngcharp tIME_string" to "static char tIME_string[30]"
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in pngtest.c (Duncan Simpson).
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Fixed a problem in pngrutil.c: gray_to_rgb didn't always work with 16-bit.
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Fixed a problem in png_read_push_finish_row(), which would not skip some
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passes that it should skip, for images that are less than 3 pixels high.
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Interchanged the order of calls to png_do_swap() and png_do_shift()
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in pngwtran.c (John Cromer).
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Added #ifdef PNG_DEBUG/#endif surrounding use of PNG_DEBUG in png.h .
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Changed "bad adaptive filter type" from error to warning in pngrutil.c .
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Fixed a documentation error about default filtering with 8-bit indexed-color.
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Separated the PNG_NO_STDIO macro into PNG_NO_STDIO and PNG_NO_CONSOLE_IO
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(L. Peter Deutsch).
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Added png_set_rgb_to_gray() and png_get_rgb_to_gray_status() functions.
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Added png_get_copyright() and png_get_header_version() functions.
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Revised comments on png_set_progressive_read_fn() in libpng.txt and example.c
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Added information about debugging in libpng.txt and libpng.3 .
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Changed "ln -sf" to "ln -s -f" in makefile.s2x, makefile.lnx, and makefile.sco.
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Removed lines after Dynamic Dependencies" in makefile.aco .
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Revised makefile.dec to make a shared library (Jeremie Petit).
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Removed trailing blanks from all files.
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Send comments/corrections/commendations to
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png-implement@dworkin.wustl.edu or to randeg@alumni.rpi.edu
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Glenn Randers-Pehrson
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libpng maintainer
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PNG Development Group
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Glenn R-P
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33
CHANGES
33
CHANGES
@ -89,7 +89,7 @@ version 0.89 [July, 1996]
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so that people are aware that they need to change their code
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changed filter selection API to allow selection of multiple filters
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since it didn't work in previous versions of libpng anyways
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optimized filter selection code
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optimized filter selection code
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fixed png_set_background() to allow using an arbitrary RGB color for
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paletted images
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fixed gamma and background correction for paletted images, so
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@ -256,7 +256,7 @@ version 0.99g [March 6, 1998, morning]
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Minor changes to pngtest.c to suppress compiler warnings.
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Removed "beta" language from documentation.
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version 0.99h [March 6, 1998, evening]
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Minor changes to previous minor changes to pngtest.c
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Minor changes to previous minor changes to pngtest.c
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Changed PNG_READ_NOT_FULLY_SUPPORTED to PNG_READ_TRANSFORMS_NOT_SUPPORTED
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and added PNG_PROGRESSIVE_READ_NOT_SUPPORTED macro
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version 1.00 [March 7, 1998]
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@ -334,7 +334,7 @@ version 1.0.1d [May 24, 1998]
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Bob Dellaca, to make a png32bd.dll with Borland C++ 4.5
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Fixed error in example.c with png_set_text: num_text is 3, not 2 (Guido V.)
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Changed several loops from count-down to count-up, for consistency.
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version 1.0.2 [June 14, 1998]
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version 1.0.1e [June 6, 1998]
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Revised libpng.txt and libpng.3 description of png_set_read|write_fn(), and
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added warnings when people try to set png_read_fn and png_write_fn in
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the same structure.
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@ -350,4 +350,29 @@ version 1.0.2 [June 14, 1998]
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and revised pngtest.c to demonstrate their use, replacing the
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PNGTEST_DEBUG_MEM feature.
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Added makefile.w32, for Microsoft C++ 4.0 and later (Tim Wegner).
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Fixed two bugs in makefile.bor
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version 1.0.2 [June 14, 1998]
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Fixed two bugs in makefile.bor .
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version 1.0.2a [December 29, 1998]
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Replaced and extended code that was removed from png_set_filler() in 1.0.1a.
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Fixed a bug in png_do_filler() that made it fail to write filler bytes in
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the left-most pixel of each row (Kevin Bracey).
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Changed "static pngcharp tIME_string" to "static char tIME_string[30]"
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in pngtest.c (Duncan Simpson).
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Fixed a problem in pngrutil.c: gray_to_rgb didn't always work with 16-bit.
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Fixed a problem in png_read_push_finish_row(), which would not skip some
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passes that it should skip, for images that are less than 3 pixels high.
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Interchanged the order of calls to png_do_swap() and png_do_shift()
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in pngwtran.c (John Cromer).
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Added #ifdef PNG_DEBUG/#endif surrounding use of PNG_DEBUG in png.h .
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Changed "bad adaptive filter type" from error to warning in pngrutil.c .
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Fixed a documentation error about default filtering with 8-bit indexed-color.
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Separated the PNG_NO_STDIO macro into PNG_NO_STDIO and PNG_NO_CONSOLE_IO
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(L. Peter Deutsch).
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Added png_set_rgb_to_gray() and png_get_rgb_to_gray_status() functions.
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Added png_get_copyright() and png_get_header_version() functions.
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Revised comments on png_set_progressive_read_fn() in libpng.txt and example.c
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Added information about debugging in libpng.txt and libpng.3 .
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Changed "ln -sf" to "ln -s -f" in makefile.s2x, makefile.lnx, and makefile.sco.
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Removed lines after Dynamic Dependencies" in makefile.aco .
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Revised makefile.dec to make a shared library (Jeremie Petit).
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Removed trailing blanks from all files.
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8
INSTALL
8
INSTALL
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Installing libpng version 1.0.2 - June 14, 1998
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Installing libpng version 1.0.2a - December 29, 1998
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Before installing libpng, you must first install zlib. zlib
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can usually be found wherever you got libpng. zlib can be
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placed in another directory, at the same level as libpng.
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Note that your system might already have a preinstalled
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zlib, but you will still need to have access to the
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zlib, but you will still need to have access to the
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zlib.h and zconf.h include files that correspond to the
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version of zlib that's installed.
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You can rename the directories that you downloaded (they
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might be called "libpng-1.0.2" or "lpng102" and "zlib-1.1.2"
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or "zlib112") so that you have directories called "zlib" and "libpng".
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might be called "libpng-1.0.2a" or "lpng103" and "zlib-1.1.3"
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or "zlib113") so that you have directories called "zlib" and "libpng".
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Your directory structure should look like this:
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73
KNOWNBUG
73
KNOWNBUG
@ -7,13 +7,80 @@ Known bugs and suggested enhancements in libpng-1.0.2
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Loops need to be optimized everywhere
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Make them count down instead of up -- Kevin Bracey
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Optimizing compilers don't need this, and making
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the change would be error prone -- Tom Lane, Glenn R-P
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Question whether i-- or --i is better.
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STATUS: Under investigation, postponed until after
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libpng-1.0.2. About 160 loops turned around
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in libpng-1.0.2a, for testing.
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libpng-1.0.2. About 160 loops will be turned around
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in libpng-1.0.Nn, for testing.
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2. June 15, 1998 -- BUG -- Evan Light
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Under some conditions, 16-bit grayscale images aren't properly
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expanded to rgb, because png_read_start_row() returns too small a
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value of max_pixel_depth when png_set_filler() has also been called.
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STATUS: Fixed in libpng-1.0.2a
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3. June 16, 1998 -- BUG -- Matt McConnell
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When reading interlaced images with a progressive reader, in some
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cases (interlaced images less than 3 pixels high) some passes are
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not skipped that should be.
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STATUS: Fixed in libpng-1.0.2a
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4. July 3, 1998 -- ENHANCEMENT -- Glenn R-P
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Added png_set_rgb_to_gray() and png_get_rgb_to_gray_status() functions.
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STATUS: Done in libpng-1.0.2a, awaiting comment on resulting test
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images.
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5. July 4, 1998 -- ENHANCEMENT -- Glenn R-P
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libpng-1.0.2 and earlier transform colors to gamma=1.0 space for
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merging with background, and then back to the image's gamma. The
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bit_depth of the intermediate (gamma=1.0) representation is probably
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not sufficient. In the typical gamma=1/2.2 situation, the linear
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pixels need about 4 more bits than the gamma-encoded ones, to avoid
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loss of precision. A similar situation exists with the rgb_to_gray
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operation.
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STATUS: under development.
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6. August 20, 1998 -- BUG -- Kevin Bracey
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When using the filler transformation, the filler isn't written
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into the leftmost pixel of each row.
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Also, the filler operation isn't being done right when writing
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files. Some code that was removed from png_set_filler() in
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libpng 1.0.1a shouldn't have been removed.
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STATUS: Fixed in libpng-1.0.2a
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7. August 23, 1998 -- BUG -- Duncan Simpson
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"static pngcharp tIME_string" should be changed to
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"static char tIME_string[30]" in pngtest.c
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STATUS: Fixed in libpng-1.0.2a
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8. August 24, 1998 -- BUG -- John Cromer
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Order of byte-swap and shift operations seems to be incorrect in
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png_do_write_transformations()
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STATUS: Under investigation.
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9. September 11, 1998 -- ENHANCEMENT -- L. Peter Deutsch
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The PNG_NO_STDIO macro should be split into PNG_NO_STDIO
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and PNG_NO_CONSOLE_STDIO.
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STATUS: Done in libpng-1.0.2a
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2
README
2
README
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README for libpng 1.0.2 - June 14, 1998 (shared library 2.1)
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README for libpng 1.0.2a - December 29, 1998 (shared library 2.1)
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See the note about version numbers near the top of png.h
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See INSTALL for instructions on how to install libpng.
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45
TODO
45
TODO
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TODO - list of things to do for libpng
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TODO - list of things to do for libpng:
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fix problem with C++ and EXTERN "C"
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add "grayscale->palette" transformation and "palette->grayscale" detection
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color to gray transformation
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improved dithering
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multi-lingual error and warning message support
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sPLT chunk handling
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cHRM transformation
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complete sRGB transformation (presently it simply uses gamma=0.45)
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man pages for function calls
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high-level API for reading images
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final bug fixes
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better documentation
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better filter selection
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(counting huffman bits/precompression? filter inertia? filter costs?)
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optional palette creation
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histogram creation
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support for application-defined chunk handlers
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keep up with public chunks
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better C++ wrapper/full C++ implementation?
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text conversion between different code pages (Latin-1 -> Mac and DOS)
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improve API by hiding the info_ptr
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Final bug fixes.
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Fix problem with C++ and EXTERN "C".
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Better C++ wrapper/full C++ implementation?
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Keep up with public chunks.
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sPLT chunk handling.
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cHRM transformation.
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Support for application-defined chunk handlers.
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Improve setjmp/longjmp usage or remove it in favor of returning error codes.
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High-level API for reading images.
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Add "grayscale->palette" transformation and "palette->grayscale" detection.
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Color to gray transformation.
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Improved dithering.
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Multi-lingual error and warning message support.
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Complete sRGB transformation (presently it simply uses gamma=0.45455).
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Man pages for function calls.
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Better documentation.
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Better filter selection
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(counting huffman bits/precompression? filter inertia? filter costs?).
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Optional palette (sPLT) creation.
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Histogram creation.
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Text conversion between different code pages (Latin-1 -> Mac and DOS).
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Improve API by hiding the info_ptr.
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18
example.c
18
example.c
@ -220,11 +220,14 @@ void read_png(FILE *fp, unsigned int sig_read) /* file is already open */
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if (png_get_sRGB(png_ptr, info_ptr, &intent))
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png_set_sRGB(png_ptr, intent, 0);
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else
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else
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{
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double image_gamma;
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if (png_get_gAMA(png_ptr, info_ptr, &image_gamma))
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png_set_gamma(png_ptr, screen_gamma, image_gamma);
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else
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png_set_gamma(png_ptr, screen_gamma, 0.50);
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png_set_gamma(png_ptr, screen_gamma, 0.45455);
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}
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/* Dither RGB files down to 8 bit palette or reduce palettes
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* to the number of colors available on your screen.
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@ -324,13 +327,13 @@ void read_png(FILE *fp, unsigned int sig_read) /* file is already open */
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{
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#ifdef sparkle /* Read the image using the "sparkle" effect. */
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png_read_rows(png_ptr, &row_pointers[y], NULL, number_of_rows);
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png_read_rows(png_ptr, NULL, row_pointers[y], number_of_rows);
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#else no_sparkle /* Read the image using the "rectangle" effect */
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png_read_rows(png_ptr, NULL, &row_pointers[y], number_of_rows);
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#endif no_sparkle /* use only one of these two methods */
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}
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/* if you want to display the image after every pass, do
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so here */
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#endif no_single /* use only one of these two methods */
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@ -384,8 +387,11 @@ initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
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return ERROR;
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}
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/* this one's new. You will need to provide all three
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/* This one's new. You will need to provide all three
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* function callbacks, even if you aren't using them all.
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* If you aren't using all functions, you can specify NULL
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* parameters. Even when all three functions are NULL,
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* you need to call png_set_progressive_read_fn().
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* These functions shouldn't be dependent on global or
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* static variables if you are decoding several images
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* simultaneously. You should store stream specific data
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@ -565,7 +571,7 @@ void write_png(char *file_name /* , ... other image information ... */)
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sig_bit.alpha = true_alpha_bit_depth;
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png_set_sBIT(png_ptr, info_ptr, sig_bit);
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/* Optional gamma chunk is strongly suggested if you have any guess
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* as to the correct gamma of the image.
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*/
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197
libpng.3
197
libpng.3
@ -1,6 +1,6 @@
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.TH LIBPNG 3 "June 14, 1998"
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.TH LIBPNG 3 "December 29, 1998"
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.SH NAME
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libpng \- Portable Network Graphics (PNG) Reference Library 1.0.2 - June 14, 1998
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libpng \- Portable Network Graphics (PNG) Reference Library 1.0.2a - December 29, 1998
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.SH SYNOPSIS
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#include <png.h>
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@ -27,7 +27,7 @@ png_structp png_create_read_struct (png_const_charp
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user_png_ver, voidp error_ptr, png_error_ptr error_fn,
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png_error_ptr warn_fn);
|
||||
|
||||
png_create_read_struct_2(png_const_charp user_png_ver,
|
||||
png_structp png_create_read_struct_2(png_const_charp user_png_ver,
|
||||
png_voidp error_ptr, png_error_ptr error_fn, png_error_ptr
|
||||
warn_fn, png_voidp mem_ptr, png_malloc_ptr malloc_fn,
|
||||
png_free_ptr free_fn)
|
||||
@ -41,8 +41,11 @@ user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
|
||||
png_error_ptr warn_fn, png_voidp mem_ptr,
|
||||
png_malloc_ptr malloc_fn, png_free_ptr free_fn)
|
||||
|
||||
png_voidp png_debug_malloc (png_structp png_ptr, png_uint_32
|
||||
size);
|
||||
int png_debug(int level, png_const_charp message)
|
||||
|
||||
int png_debug1(int level, png_const_charp message, p1)
|
||||
|
||||
int png_debug2(int level, png_const_charp message, p1, p2)
|
||||
|
||||
void png_destroy_info_struct (png_structp png_ptr, png_infopp
|
||||
info_ptr_ptr);
|
||||
@ -79,6 +82,8 @@ info_ptr);
|
||||
png_byte png_get_compression_type (png_structp png_ptr,
|
||||
png_infop info_ptr);
|
||||
|
||||
png_byte png_get_copyright (png_structp png_ptr);
|
||||
|
||||
png_voidp png_get_error_ptr (png_structp png_ptr);
|
||||
|
||||
png_byte png_get_filter_type (png_structp png_ptr, png_infop
|
||||
@ -87,6 +92,8 @@ info_ptr);
|
||||
png_uint_32 png_get_gAMA (png_structp png_ptr, png_infop
|
||||
info_ptr, double *file_gamma);
|
||||
|
||||
png_byte png_get_header_version (png_structp png_ptr);
|
||||
|
||||
png_uint_32 png_get_hIST (png_structp png_ptr, png_infop
|
||||
info_ptr, png_uint_16p *hist);
|
||||
|
||||
@ -131,6 +138,8 @@ png_voidp png_get_progressive_ptr (png_structp png_ptr);
|
||||
png_uint_32 png_get_PLTE (png_structp png_ptr, png_infop
|
||||
info_ptr, png_colorp *palette, int *num_palette);
|
||||
|
||||
png_byte png_get_rgb_to_gray_status (png_structp png_ptr)
|
||||
|
||||
png_uint_32 png_get_rowbytes (png_structp png_ptr, png_infop
|
||||
info_ptr);
|
||||
|
||||
@ -325,7 +334,7 @@ read_row_fn);
|
||||
void png_set_read_user_transform_fn (png_structp png_ptr,
|
||||
png_user_transform_ptr read_user_transform_fn);
|
||||
|
||||
void png_set_rgb_to_gray (png_structp png_ptr);
|
||||
void png_set_rgb_to_gray (png_structp png_ptr, int error_action);
|
||||
|
||||
void png_set_sBIT (png_structp png_ptr, png_infop info_ptr,
|
||||
png_color_8p sig_bit);
|
||||
@ -414,7 +423,7 @@ Following is a copy of the libpng.txt file that accompanies libpng.
|
||||
.SH LIBPNG.TXT
|
||||
libpng.txt - A description on how to use and modify libpng
|
||||
|
||||
libpng version 1.0.2 - June 14, 1998
|
||||
libpng version 1.0.2a - December 29, 1998
|
||||
Updated and distributed by Glenn Randers-Pehrson
|
||||
<randeg@alumni.rpi.edu>
|
||||
Copyright (c) 1998, Glenn Randers-Pehrson
|
||||
@ -424,7 +433,7 @@ libpng.txt - A description on how to use and modify libpng
|
||||
based on:
|
||||
|
||||
libpng 1.0 beta 6 version 0.96 May 28, 1997
|
||||
Updated and distributed by Andreas Dilger
|
||||
Updated and distributed by Andreas Dilger
|
||||
Copyright (c) 1996, 1997 Andreas Dilger
|
||||
|
||||
libpng 1.0 beta 2 - version 0.88 January 26, 1996
|
||||
@ -454,7 +463,8 @@ 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
|
||||
about PNG can be found at the PNG home page, <http://www.cdrom.com/pub/png/>.
|
||||
about PNG, and the latest version of libpng, can be found at the PNG home
|
||||
page, <http://www.cdrom.com/pub/png/>.
|
||||
|
||||
Most users will not have to modify the library significantly; advanced
|
||||
users may want to modify it more. All attempts were made to make it as
|
||||
@ -471,6 +481,8 @@ work to be done (see the TODO file), libpng should cover the
|
||||
majority of the needs of its users.
|
||||
|
||||
Libpng uses zlib for its compression and decompression of PNG files.
|
||||
Further information about zlib, and the latest version of zlib, can
|
||||
be found at the zlib home page, <http://www.cdrom.com/pub/infozip/zlib/>.
|
||||
The zlib compression utility is a general purpose utility that is
|
||||
useful for more than PNG files, and can be used without libpng.
|
||||
See the documentation delivered with zlib for more details.
|
||||
@ -593,8 +605,8 @@ are only necessary if you are not using the libpng supplied error
|
||||
handling and memory alloc/free functions.
|
||||
|
||||
When libpng encounters an error, it expects to longjmp back
|
||||
to your routine. Therefore, you will need to call setjmp and pass the
|
||||
jmpbuf field of your png_struct. If you read the file from different
|
||||
to your routine. Therefore, you will need to call setjmp and pass
|
||||
your png_ptr->jmpbuf. If you read the file from different
|
||||
routines, you will need to update the jmpbuf field every time you enter
|
||||
a new routine that will call a png_ function.
|
||||
|
||||
@ -667,7 +679,7 @@ with
|
||||
You must supply the function
|
||||
|
||||
void read_transform_fn(png_ptr ptr, row_info_ptr
|
||||
row_info, png_bytep data)
|
||||
row_info, png_bytep data)
|
||||
|
||||
See pngtest.c for a working example. Your function will be called
|
||||
after all of the other transformations have been processed.
|
||||
@ -696,7 +708,7 @@ Functions are used to get the information from the info_ptr:
|
||||
are present.
|
||||
PNG_COLOR_TYPE_GRAY
|
||||
(bit depths 1, 2, 4, 8, 16)
|
||||
PNG_COLOR_TYPE_GRAY_ALPHA
|
||||
PNG_COLOR_TYPE_GRAY_ALPHA
|
||||
(bit depths 8, 16)
|
||||
PNG_COLOR_TYPE_PALETTE
|
||||
(bit depths 1, 2, 4, 8)
|
||||
@ -1002,6 +1014,63 @@ RGB. This code will do that conversion:
|
||||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
|
||||
png_set_gray_to_rgb(png_ptr);
|
||||
|
||||
Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
|
||||
with alpha. This is intended for conversion of images that really are
|
||||
gray (red == green == blue), so the function simply strips out the red
|
||||
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);
|
||||
|
||||
error_action = 1: silently do the conversion
|
||||
error_action = 2: issue a warning if the original
|
||||
image has any pixel where
|
||||
red != green or red != blue
|
||||
error_action = 3: issue an error and abort the
|
||||
conversion if the original
|
||||
image has any pixel where
|
||||
red != green or red != blue
|
||||
|
||||
red_weight: weight of red component
|
||||
(NULL -> default 54/256)
|
||||
green_weight: weight of green component
|
||||
(NULL -> default 183/256)
|
||||
|
||||
If you have set error_action = 1 or 2, you can
|
||||
later check whether the image really was gray, after processing
|
||||
the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
|
||||
It will return a png_byte that is zero if the image was gray or
|
||||
1 if there were any non-gray pixels. bKGD and sBIT data
|
||||
will be silently converted to grayscale, using the green channel
|
||||
data, regardless of the error_action setting.
|
||||
|
||||
With 0.0<=red_weight+green_weight<=1.0,
|
||||
the normalized graylevel is computed:
|
||||
|
||||
int rw = red_weight * 256;
|
||||
int gw = green_weight * 256;
|
||||
int bw = 256 - (rw + gw);
|
||||
gray = (rw*red + gw*green + bw*blue)/256;
|
||||
|
||||
The default values approximate those recommended in the Charles
|
||||
Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
|
||||
Copyright (c) 1998-01-04 Charles Poynton poynton@inforamp.net
|
||||
|
||||
Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
|
||||
|
||||
Libpng approximates this with
|
||||
|
||||
Y = 0.211 * R + 0.715 * G + 0.074 * B
|
||||
|
||||
which can be expressed with integers as
|
||||
|
||||
Y = (54 * R + 183 * G + 19 * B)/256
|
||||
|
||||
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
|
||||
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
|
||||
@ -1061,7 +1130,7 @@ compensation other than the display_gamma is needed (viewing_gamma=1.0).
|
||||
The png_set_gamma() function handles gamma transformations of the data.
|
||||
Pass both the file gamma and the current screen_gamma. If the file does
|
||||
not have a gamma value, you can pass one anyway if you have an idea what
|
||||
it is (usually 0.50 is a good guess for GIF images on PCs). Note
|
||||
it is (usually 0.45455 is a good guess for GIF images on PCs). Note
|
||||
that file gammas are inverted from screen gammas. See the discussions
|
||||
on gamma in the PNG specification for an excellent description of what
|
||||
gamma is, and why all applications should support it. It is strongly
|
||||
@ -1070,7 +1139,7 @@ recommended that PNG viewers support gamma correction.
|
||||
if (png_get_gAMA(png_ptr, info_ptr, &gamma))
|
||||
png_set_gamma(png_ptr, screen_gamma, gamma);
|
||||
else
|
||||
png_set_gamma(png_ptr, screen_gamma, 0.50);
|
||||
png_set_gamma(png_ptr, screen_gamma, 0.45455);
|
||||
|
||||
If you need to reduce an RGB file to a paletted file, or if a paletted
|
||||
file has more entries then will fit on your screen, png_set_dither()
|
||||
@ -1321,7 +1390,9 @@ png_infop info_ptr;
|
||||
to be called when the header info is valid,
|
||||
when each row is completed, and when the image
|
||||
is finished. If you aren't using all functions,
|
||||
you can specify a NULL parameter. You can use
|
||||
you can specify NULL parameters. Even when all
|
||||
three functions are NULL, you need to call
|
||||
png_set_progressive_read_fn(). You can use
|
||||
any struct as the user_ptr (cast to a void pointer
|
||||
for the function call), and retrieve the pointer
|
||||
from inside the callbacks using the function
|
||||
@ -1353,21 +1424,21 @@ png_infop info_ptr;
|
||||
of data from the file stream (in order, of
|
||||
course). On machines with segmented memory
|
||||
models machines, don't give it any more than
|
||||
64K. The library seems to run fine with sizes
|
||||
64K. The library seems to run fine with sizes
|
||||
of 4K. Although you can give it much less if
|
||||
necessary (I assume you can give it chunks of
|
||||
1 byte, I haven't tried less then 256 bytes
|
||||
yet). When this function returns, you may
|
||||
want to display any rows that were generated
|
||||
in the row callback if you don't already do
|
||||
so there.
|
||||
so there.
|
||||
*/
|
||||
png_process_data(png_ptr, info_ptr, buffer, length);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* This function is called (as set by
|
||||
png_set_progressive_fn() above) when enough data
|
||||
png_set_progressive_read_fn() above) when enough data
|
||||
has been supplied so all of the header has been
|
||||
read.
|
||||
*/
|
||||
@ -1424,7 +1495,7 @@ png_infop info_ptr;
|
||||
for interlaced images), you will have to pass
|
||||
the current row, and the function will combine
|
||||
the old row and the new row.
|
||||
*/
|
||||
*/
|
||||
}
|
||||
|
||||
void
|
||||
@ -1454,7 +1525,7 @@ You will want to do the I/O initialization before you get into libpng,
|
||||
so if it doesn't work, you don't have anything to undo. If you are not
|
||||
using the standard I/O functions, you will need to replace them with
|
||||
custom writing functions. See the discussion under Customizing libpng.
|
||||
|
||||
|
||||
FILE *fp = fopen(file_name, "wb");
|
||||
if (!fp)
|
||||
{
|
||||
@ -1495,20 +1566,22 @@ png_create_write_struct_2() instead of png_create_read_struct():
|
||||
After you have these structures, you will need to set up the
|
||||
error handling. When libpng encounters an error, it expects to
|
||||
longjmp() back to your routine. Therefore, you will need to call
|
||||
setjmp and pass the jmpbuf field of your png_struct. If you
|
||||
setjmp() and pass the png_ptr->jmpbuf. If you
|
||||
write the file from different routines, you will need to update
|
||||
the jmpbuf field every time you enter a new routine that will
|
||||
call a png_ function. See your documentation of setjmp/longjmp
|
||||
for your compiler for more information on setjmp/longjmp. See
|
||||
the discussion on libpng error handling in the Customizing Libpng
|
||||
section below for more information on the libpng error handling.
|
||||
|
||||
|
||||
if (setjmp(png_ptr->jmpbuf))
|
||||
{
|
||||
{
|
||||
png_destroy_write_struct(&png_ptr, &info_ptr);
|
||||
fclose(fp);
|
||||
return;
|
||||
}
|
||||
...
|
||||
return;
|
||||
|
||||
Now you need to set up the output code. The default for libpng is to
|
||||
use the C function fwrite(). If you use this, you will need to pass a
|
||||
@ -1549,7 +1622,7 @@ 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.
|
||||
|
||||
|
||||
|
||||
/* turn on or off filtering, and/or choose
|
||||
specific filters */
|
||||
png_set_filter(png_ptr, 0,
|
||||
@ -1648,7 +1721,7 @@ Some of the more important parts of the png_info are:
|
||||
PNG_SRGB_INTENT_PERCEPTUAL,
|
||||
PNG_SRGB_INTENT_ABSOLUTE, or
|
||||
PNG_SRGB_INTENT_RELATIVE.
|
||||
|
||||
|
||||
|
||||
png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
|
||||
srgb_intent);
|
||||
@ -1739,7 +1812,7 @@ png_text structure holds a keyword-text value, and a compression type.
|
||||
The compression types have the same valid numbers as the compression
|
||||
types of the image data. Currently, the only valid number is zero.
|
||||
However, you can store text either compressed or uncompressed, unlike
|
||||
images which always have to be compressed. So if you don't want the
|
||||
images, which always have to be compressed. So if you don't want the
|
||||
text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
|
||||
Until text gets around 1000 bytes, it is not worth compressing it.
|
||||
After the text has been written out to the file, the compression type
|
||||
@ -1799,7 +1872,7 @@ depending on whether you mean the PNG file, the time the image was
|
||||
created in a non-PNG format, a still photo from which the image was
|
||||
scanned, or possibly the subject matter itself. In order to facilitate
|
||||
machine-readable dates, it is recommended that the "Creation Time"
|
||||
tEXt chunk use RFC 1123 format dates (e.g. 22 May 1997 18:07:10 GMT"),
|
||||
tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"),
|
||||
although this isn't a requirement. Unlike the tIME chunk, the
|
||||
"Creation Time" tEXt chunk is not expected to be automatically changed
|
||||
by the software. To facilitate the use of RFC 1123 dates, a function
|
||||
@ -1841,7 +1914,7 @@ correctly pack the pixels into a single byte:
|
||||
PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
|
||||
data is of another bit depth, you can write an sBIT chunk into the
|
||||
file so that decoders can get the original data if desired.
|
||||
|
||||
|
||||
/* Set the true bit depth of the image data */
|
||||
if (color_type & PNG_COLOR_MASK_COLOR)
|
||||
{
|
||||
@ -1902,7 +1975,7 @@ with
|
||||
You must supply the function
|
||||
|
||||
void write_transform_fn(png_ptr ptr, row_info_ptr
|
||||
row_info, png_bytep data)
|
||||
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.
|
||||
@ -2017,7 +2090,7 @@ The second deals with more complicated things like adding new chunks,
|
||||
adding new transformations, and generally changing how libpng works.
|
||||
|
||||
All of the memory allocation, input/output, and error handling in libpng
|
||||
goes through callbacks which are user settable. The default routines are
|
||||
goes through callbacks that are user settable. The default routines are
|
||||
in pngmem.c, pngrio.c, pngwio.c, and pngerror.c respectively. To change
|
||||
these functions, call the appropriate png_set_???_fn() function.
|
||||
|
||||
@ -2059,7 +2132,7 @@ The replacement I/O functions should have prototypes as follows:
|
||||
|
||||
Supplying NULL for the read, write, or flush functions sets them back
|
||||
to using the default C stream functions. It is an error to read from
|
||||
a write stream, and vice versa.
|
||||
a write stream, and vice versa.
|
||||
|
||||
Error handling in libpng is done through png_error() and png_warning().
|
||||
Errors handled through png_error() are fatal, meaning that png_error()
|
||||
@ -2126,7 +2199,7 @@ won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K.
|
||||
|
||||
Configuring for DOS:
|
||||
|
||||
For DOS users which only have access to the lower 640K, you will
|
||||
For DOS users who only have access to the lower 640K, you will
|
||||
have to limit zlib's memory usage via a png_set_compression_mem_level()
|
||||
call. See zlib.h or zconf.h in the zlib library for more information.
|
||||
|
||||
@ -2138,7 +2211,7 @@ defined, and FAR gets defined to far in pngconf.h, and you should be
|
||||
all set. Everything in the library (except for zlib's structure) is
|
||||
expecting far data. You must use the typedefs with the p or pp on
|
||||
the end for pointers (or at least look at them and be careful). Make
|
||||
note that the row's of data are defined as png_bytepp which is a
|
||||
note that the row's of data are defined as png_bytepp, which is an
|
||||
unsigned char far * far *.
|
||||
|
||||
Configuring for gui/windowing platforms:
|
||||
@ -2198,8 +2271,8 @@ can call one of these functions. The selection and configuration
|
||||
of row filters can have a significant impact on the size and
|
||||
encoding speed and a somewhat lesser impact on the decoding speed
|
||||
of an image. Filtering is enabled by default for RGB and grayscale
|
||||
images (with and without alpha), and for 8-bit paletted images, but
|
||||
not for paletted images with bit depths less than 8 bits/pixel.
|
||||
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'
|
||||
@ -2234,10 +2307,10 @@ by telling it the relative computational costs of the filters.
|
||||
PNG_FILTER_SELECTION_WEIGHTED, 3,
|
||||
weights, costs);
|
||||
|
||||
The weights are multiplying factors which indicate to libpng that row
|
||||
should be the same for successive rows unless another row filter is that
|
||||
many times better than the previous filter. In the above example, if
|
||||
the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
|
||||
The weights are multiplying factors that indicate to libpng that the
|
||||
row filter should be the same for successive rows unless another row filter
|
||||
is that many times better than the previous filter. In the above example,
|
||||
if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
|
||||
"sum of absolute differences" 1.5 x 1.3 times higher than other filters
|
||||
and still be chosen, while the NONE filter could have a sum 1.1 times
|
||||
higher than other filters and still be chosen. Unspecified weights are
|
||||
@ -2292,10 +2365,46 @@ or DLL file), you should not remove or disable any parts of the library,
|
||||
as this will cause applications linked with different versions of the
|
||||
library to fail if they call functions not available in your library.
|
||||
The size of the library itself should not be an issue, because only
|
||||
those sections which are actually used will be loaded into memory.
|
||||
those sections that are actually used will be loaded into memory.
|
||||
|
||||
Requesting debug printout:
|
||||
|
||||
Changes to Libpng from version 0.88
|
||||
The macro definition PNG_DEBUG can be used to request debugging
|
||||
printout. Set it to an integer value in the range 0 to 3. Higher
|
||||
numbers result in increasing amounts of debugging information. The
|
||||
information is printed to the "stderr" file, unless another file
|
||||
name is specified in the PNG_DEBUG_FILE macro definition.
|
||||
|
||||
When PNG_DEBUG > 0, the following functions (macros) become available:
|
||||
|
||||
png_debug(level, message)
|
||||
png_debug1(level, message, p1)
|
||||
png_debug2(level, message, p1, p2)
|
||||
|
||||
in which "level" is compared to PNG_DEBUG to decide whether to print
|
||||
the message, "message" is the formatted string to be printed,
|
||||
and p1 and p2 are parameters that are to be embedded in the string
|
||||
according to printf-style formatting directives. For example,
|
||||
|
||||
png_debug1(2, "foo=%d\n", foo);
|
||||
|
||||
is expanded to
|
||||
|
||||
if(PNG_DEBUG > 2)
|
||||
fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
|
||||
|
||||
When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
|
||||
can still use PNG_DEBUG to control your own debugging:
|
||||
|
||||
#ifdef PNG_DEBUG
|
||||
fprintf(stderr, ...
|
||||
#endif
|
||||
|
||||
When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
|
||||
having level = 0 will be printed. There aren't any such statements in
|
||||
this version of libpng, but if you insert some they will be printed.
|
||||
|
||||
.SH VI. Changes to Libpng from version 0.88
|
||||
|
||||
It should be noted that versions of libpng later than 0.96 are not
|
||||
distributed by the original libpng author, Guy Schalnat, nor by
|
||||
@ -2321,7 +2430,7 @@ allocating and freeing the png_struct for each image read.
|
||||
|
||||
Setting the error callbacks via png_set_message_fn() before
|
||||
png_read_init() as was suggested in libpng-0.88 is no longer supported
|
||||
because this caused applications which do not use custom error functions
|
||||
because this caused applications that do not use custom error functions
|
||||
to fail if the png_ptr was not initialized to zero. It is still possible
|
||||
to set the error callbacks AFTER png_read_init(), or to change them with
|
||||
png_set_error_fn(), which is essentially the same function, but with a
|
||||
@ -2413,7 +2522,7 @@ possible without all of you.
|
||||
|
||||
Thanks to Frank J. T. Wojcik for helping with the documentation.
|
||||
|
||||
Libpng version 1.0.2 - June 14, 1998:
|
||||
Libpng version 1.0.2a - December 29, 1998:
|
||||
Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
|
||||
Currently maintained by Glenn Randers-Pehrson (randeg@alumni.rpi.edu).
|
||||
|
||||
|
174
libpng.txt
174
libpng.txt
@ -1,6 +1,6 @@
|
||||
libpng.txt - A description on how to use and modify libpng
|
||||
|
||||
libpng version 1.0.2 - June 14, 1998
|
||||
libpng version 1.0.2a - December 29, 1998
|
||||
Updated and distributed by Glenn Randers-Pehrson
|
||||
<randeg@alumni.rpi.edu>
|
||||
Copyright (c) 1998, Glenn Randers-Pehrson
|
||||
@ -10,7 +10,7 @@ libpng.txt - A description on how to use and modify libpng
|
||||
based on:
|
||||
|
||||
libpng 1.0 beta 6 version 0.96 May 28, 1997
|
||||
Updated and distributed by Andreas Dilger
|
||||
Updated and distributed by Andreas Dilger
|
||||
Copyright (c) 1996, 1997 Andreas Dilger
|
||||
|
||||
libpng 1.0 beta 2 - version 0.88 January 26, 1996
|
||||
@ -40,7 +40,8 @@ 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
|
||||
about PNG can be found at the PNG home page, <http://www.cdrom.com/pub/png/>.
|
||||
about PNG, and the latest version of libpng, can be found at the PNG home
|
||||
page, <http://www.cdrom.com/pub/png/>.
|
||||
|
||||
Most users will not have to modify the library significantly; advanced
|
||||
users may want to modify it more. All attempts were made to make it as
|
||||
@ -57,6 +58,8 @@ work to be done (see the TODO file), libpng should cover the
|
||||
majority of the needs of its users.
|
||||
|
||||
Libpng uses zlib for its compression and decompression of PNG files.
|
||||
Further information about zlib, and the latest version of zlib, can
|
||||
be found at the zlib home page, <http://www.cdrom.com/pub/infozip/zlib/>.
|
||||
The zlib compression utility is a general purpose utility that is
|
||||
useful for more than PNG files, and can be used without libpng.
|
||||
See the documentation delivered with zlib for more details.
|
||||
@ -179,8 +182,8 @@ are only necessary if you are not using the libpng supplied error
|
||||
handling and memory alloc/free functions.
|
||||
|
||||
When libpng encounters an error, it expects to longjmp back
|
||||
to your routine. Therefore, you will need to call setjmp and pass the
|
||||
jmpbuf field of your png_struct. If you read the file from different
|
||||
to your routine. Therefore, you will need to call setjmp and pass
|
||||
your png_ptr->jmpbuf. If you read the file from different
|
||||
routines, you will need to update the jmpbuf field every time you enter
|
||||
a new routine that will call a png_ function.
|
||||
|
||||
@ -253,7 +256,7 @@ with
|
||||
You must supply the function
|
||||
|
||||
void read_transform_fn(png_ptr ptr, row_info_ptr
|
||||
row_info, png_bytep data)
|
||||
row_info, png_bytep data)
|
||||
|
||||
See pngtest.c for a working example. Your function will be called
|
||||
after all of the other transformations have been processed.
|
||||
@ -282,7 +285,7 @@ Functions are used to get the information from the info_ptr:
|
||||
are present.
|
||||
PNG_COLOR_TYPE_GRAY
|
||||
(bit depths 1, 2, 4, 8, 16)
|
||||
PNG_COLOR_TYPE_GRAY_ALPHA
|
||||
PNG_COLOR_TYPE_GRAY_ALPHA
|
||||
(bit depths 8, 16)
|
||||
PNG_COLOR_TYPE_PALETTE
|
||||
(bit depths 1, 2, 4, 8)
|
||||
@ -588,6 +591,63 @@ RGB. This code will do that conversion:
|
||||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
|
||||
png_set_gray_to_rgb(png_ptr);
|
||||
|
||||
Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
|
||||
with alpha. This is intended for conversion of images that really are
|
||||
gray (red == green == blue), so the function simply strips out the red
|
||||
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);
|
||||
|
||||
error_action = 1: silently do the conversion
|
||||
error_action = 2: issue a warning if the original
|
||||
image has any pixel where
|
||||
red != green or red != blue
|
||||
error_action = 3: issue an error and abort the
|
||||
conversion if the original
|
||||
image has any pixel where
|
||||
red != green or red != blue
|
||||
|
||||
red_weight: weight of red component
|
||||
(NULL -> default 54/256)
|
||||
green_weight: weight of green component
|
||||
(NULL -> default 183/256)
|
||||
|
||||
If you have set error_action = 1 or 2, you can
|
||||
later check whether the image really was gray, after processing
|
||||
the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
|
||||
It will return a png_byte that is zero if the image was gray or
|
||||
1 if there were any non-gray pixels. bKGD and sBIT data
|
||||
will be silently converted to grayscale, using the green channel
|
||||
data, regardless of the error_action setting.
|
||||
|
||||
With 0.0<=red_weight+green_weight<=1.0,
|
||||
the normalized graylevel is computed:
|
||||
|
||||
int rw = red_weight * 256;
|
||||
int gw = green_weight * 256;
|
||||
int bw = 256 - (rw + gw);
|
||||
gray = (rw*red + gw*green + bw*blue)/256;
|
||||
|
||||
The default values approximate those recommended in the Charles
|
||||
Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
|
||||
Copyright (c) 1998-01-04 Charles Poynton poynton@inforamp.net
|
||||
|
||||
Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
|
||||
|
||||
Libpng approximates this with
|
||||
|
||||
Y = 0.211 * R + 0.715 * G + 0.074 * B
|
||||
|
||||
which can be expressed with integers as
|
||||
|
||||
Y = (54 * R + 183 * G + 19 * B)/256
|
||||
|
||||
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
|
||||
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
|
||||
@ -647,7 +707,7 @@ compensation other than the display_gamma is needed (viewing_gamma=1.0).
|
||||
The png_set_gamma() function handles gamma transformations of the data.
|
||||
Pass both the file gamma and the current screen_gamma. If the file does
|
||||
not have a gamma value, you can pass one anyway if you have an idea what
|
||||
it is (usually 0.50 is a good guess for GIF images on PCs). Note
|
||||
it is (usually 0.45455 is a good guess for GIF images on PCs). Note
|
||||
that file gammas are inverted from screen gammas. See the discussions
|
||||
on gamma in the PNG specification for an excellent description of what
|
||||
gamma is, and why all applications should support it. It is strongly
|
||||
@ -656,7 +716,7 @@ recommended that PNG viewers support gamma correction.
|
||||
if (png_get_gAMA(png_ptr, info_ptr, &gamma))
|
||||
png_set_gamma(png_ptr, screen_gamma, gamma);
|
||||
else
|
||||
png_set_gamma(png_ptr, screen_gamma, 0.50);
|
||||
png_set_gamma(png_ptr, screen_gamma, 0.45455);
|
||||
|
||||
If you need to reduce an RGB file to a paletted file, or if a paletted
|
||||
file has more entries then will fit on your screen, png_set_dither()
|
||||
@ -907,7 +967,9 @@ png_infop info_ptr;
|
||||
to be called when the header info is valid,
|
||||
when each row is completed, and when the image
|
||||
is finished. If you aren't using all functions,
|
||||
you can specify a NULL parameter. You can use
|
||||
you can specify NULL parameters. Even when all
|
||||
three functions are NULL, you need to call
|
||||
png_set_progressive_read_fn(). You can use
|
||||
any struct as the user_ptr (cast to a void pointer
|
||||
for the function call), and retrieve the pointer
|
||||
from inside the callbacks using the function
|
||||
@ -939,21 +1001,21 @@ png_infop info_ptr;
|
||||
of data from the file stream (in order, of
|
||||
course). On machines with segmented memory
|
||||
models machines, don't give it any more than
|
||||
64K. The library seems to run fine with sizes
|
||||
64K. The library seems to run fine with sizes
|
||||
of 4K. Although you can give it much less if
|
||||
necessary (I assume you can give it chunks of
|
||||
1 byte, I haven't tried less then 256 bytes
|
||||
yet). When this function returns, you may
|
||||
want to display any rows that were generated
|
||||
in the row callback if you don't already do
|
||||
so there.
|
||||
so there.
|
||||
*/
|
||||
png_process_data(png_ptr, info_ptr, buffer, length);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* This function is called (as set by
|
||||
png_set_progressive_fn() above) when enough data
|
||||
png_set_progressive_read_fn() above) when enough data
|
||||
has been supplied so all of the header has been
|
||||
read.
|
||||
*/
|
||||
@ -1010,7 +1072,7 @@ png_infop info_ptr;
|
||||
for interlaced images), you will have to pass
|
||||
the current row, and the function will combine
|
||||
the old row and the new row.
|
||||
*/
|
||||
*/
|
||||
}
|
||||
|
||||
void
|
||||
@ -1040,7 +1102,7 @@ You will want to do the I/O initialization before you get into libpng,
|
||||
so if it doesn't work, you don't have anything to undo. If you are not
|
||||
using the standard I/O functions, you will need to replace them with
|
||||
custom writing functions. See the discussion under Customizing libpng.
|
||||
|
||||
|
||||
FILE *fp = fopen(file_name, "wb");
|
||||
if (!fp)
|
||||
{
|
||||
@ -1081,20 +1143,22 @@ png_create_write_struct_2() instead of png_create_read_struct():
|
||||
After you have these structures, you will need to set up the
|
||||
error handling. When libpng encounters an error, it expects to
|
||||
longjmp() back to your routine. Therefore, you will need to call
|
||||
setjmp and pass the jmpbuf field of your png_struct. If you
|
||||
setjmp() and pass the png_ptr->jmpbuf. If you
|
||||
write the file from different routines, you will need to update
|
||||
the jmpbuf field every time you enter a new routine that will
|
||||
call a png_ function. See your documentation of setjmp/longjmp
|
||||
for your compiler for more information on setjmp/longjmp. See
|
||||
the discussion on libpng error handling in the Customizing Libpng
|
||||
section below for more information on the libpng error handling.
|
||||
|
||||
|
||||
if (setjmp(png_ptr->jmpbuf))
|
||||
{
|
||||
{
|
||||
png_destroy_write_struct(&png_ptr, &info_ptr);
|
||||
fclose(fp);
|
||||
return;
|
||||
}
|
||||
...
|
||||
return;
|
||||
|
||||
Now you need to set up the output code. The default for libpng is to
|
||||
use the C function fwrite(). If you use this, you will need to pass a
|
||||
@ -1135,7 +1199,7 @@ 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.
|
||||
|
||||
|
||||
|
||||
/* turn on or off filtering, and/or choose
|
||||
specific filters */
|
||||
png_set_filter(png_ptr, 0,
|
||||
@ -1234,7 +1298,7 @@ Some of the more important parts of the png_info are:
|
||||
PNG_SRGB_INTENT_PERCEPTUAL,
|
||||
PNG_SRGB_INTENT_ABSOLUTE, or
|
||||
PNG_SRGB_INTENT_RELATIVE.
|
||||
|
||||
|
||||
|
||||
png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
|
||||
srgb_intent);
|
||||
@ -1325,7 +1389,7 @@ png_text structure holds a keyword-text value, and a compression type.
|
||||
The compression types have the same valid numbers as the compression
|
||||
types of the image data. Currently, the only valid number is zero.
|
||||
However, you can store text either compressed or uncompressed, unlike
|
||||
images which always have to be compressed. So if you don't want the
|
||||
images, which always have to be compressed. So if you don't want the
|
||||
text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
|
||||
Until text gets around 1000 bytes, it is not worth compressing it.
|
||||
After the text has been written out to the file, the compression type
|
||||
@ -1385,7 +1449,7 @@ depending on whether you mean the PNG file, the time the image was
|
||||
created in a non-PNG format, a still photo from which the image was
|
||||
scanned, or possibly the subject matter itself. In order to facilitate
|
||||
machine-readable dates, it is recommended that the "Creation Time"
|
||||
tEXt chunk use RFC 1123 format dates (e.g. 22 May 1997 18:07:10 GMT"),
|
||||
tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"),
|
||||
although this isn't a requirement. Unlike the tIME chunk, the
|
||||
"Creation Time" tEXt chunk is not expected to be automatically changed
|
||||
by the software. To facilitate the use of RFC 1123 dates, a function
|
||||
@ -1427,7 +1491,7 @@ correctly pack the pixels into a single byte:
|
||||
PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
|
||||
data is of another bit depth, you can write an sBIT chunk into the
|
||||
file so that decoders can get the original data if desired.
|
||||
|
||||
|
||||
/* Set the true bit depth of the image data */
|
||||
if (color_type & PNG_COLOR_MASK_COLOR)
|
||||
{
|
||||
@ -1488,7 +1552,7 @@ with
|
||||
You must supply the function
|
||||
|
||||
void write_transform_fn(png_ptr ptr, row_info_ptr
|
||||
row_info, png_bytep data)
|
||||
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.
|
||||
@ -1603,7 +1667,7 @@ The second deals with more complicated things like adding new chunks,
|
||||
adding new transformations, and generally changing how libpng works.
|
||||
|
||||
All of the memory allocation, input/output, and error handling in libpng
|
||||
goes through callbacks which are user settable. The default routines are
|
||||
goes through callbacks that are user settable. The default routines are
|
||||
in pngmem.c, pngrio.c, pngwio.c, and pngerror.c respectively. To change
|
||||
these functions, call the appropriate png_set_???_fn() function.
|
||||
|
||||
@ -1645,7 +1709,7 @@ The replacement I/O functions should have prototypes as follows:
|
||||
|
||||
Supplying NULL for the read, write, or flush functions sets them back
|
||||
to using the default C stream functions. It is an error to read from
|
||||
a write stream, and vice versa.
|
||||
a write stream, and vice versa.
|
||||
|
||||
Error handling in libpng is done through png_error() and png_warning().
|
||||
Errors handled through png_error() are fatal, meaning that png_error()
|
||||
@ -1712,7 +1776,7 @@ won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K.
|
||||
|
||||
Configuring for DOS:
|
||||
|
||||
For DOS users which only have access to the lower 640K, you will
|
||||
For DOS users who only have access to the lower 640K, you will
|
||||
have to limit zlib's memory usage via a png_set_compression_mem_level()
|
||||
call. See zlib.h or zconf.h in the zlib library for more information.
|
||||
|
||||
@ -1724,7 +1788,7 @@ defined, and FAR gets defined to far in pngconf.h, and you should be
|
||||
all set. Everything in the library (except for zlib's structure) is
|
||||
expecting far data. You must use the typedefs with the p or pp on
|
||||
the end for pointers (or at least look at them and be careful). Make
|
||||
note that the row's of data are defined as png_bytepp which is a
|
||||
note that the row's of data are defined as png_bytepp, which is an
|
||||
unsigned char far * far *.
|
||||
|
||||
Configuring for gui/windowing platforms:
|
||||
@ -1784,8 +1848,8 @@ can call one of these functions. The selection and configuration
|
||||
of row filters can have a significant impact on the size and
|
||||
encoding speed and a somewhat lesser impact on the decoding speed
|
||||
of an image. Filtering is enabled by default for RGB and grayscale
|
||||
images (with and without alpha), and for 8-bit paletted images, but
|
||||
not for paletted images with bit depths less than 8 bits/pixel.
|
||||
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'
|
||||
@ -1820,10 +1884,10 @@ by telling it the relative computational costs of the filters.
|
||||
PNG_FILTER_SELECTION_WEIGHTED, 3,
|
||||
weights, costs);
|
||||
|
||||
The weights are multiplying factors which indicate to libpng that row
|
||||
should be the same for successive rows unless another row filter is that
|
||||
many times better than the previous filter. In the above example, if
|
||||
the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
|
||||
The weights are multiplying factors that indicate to libpng that the
|
||||
row filter should be the same for successive rows unless another row filter
|
||||
is that many times better than the previous filter. In the above example,
|
||||
if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
|
||||
"sum of absolute differences" 1.5 x 1.3 times higher than other filters
|
||||
and still be chosen, while the NONE filter could have a sum 1.1 times
|
||||
higher than other filters and still be chosen. Unspecified weights are
|
||||
@ -1878,10 +1942,46 @@ or DLL file), you should not remove or disable any parts of the library,
|
||||
as this will cause applications linked with different versions of the
|
||||
library to fail if they call functions not available in your library.
|
||||
The size of the library itself should not be an issue, because only
|
||||
those sections which are actually used will be loaded into memory.
|
||||
those sections that are actually used will be loaded into memory.
|
||||
|
||||
Requesting debug printout:
|
||||
|
||||
Changes to Libpng from version 0.88
|
||||
The macro definition PNG_DEBUG can be used to request debugging
|
||||
printout. Set it to an integer value in the range 0 to 3. Higher
|
||||
numbers result in increasing amounts of debugging information. The
|
||||
information is printed to the "stderr" file, unless another file
|
||||
name is specified in the PNG_DEBUG_FILE macro definition.
|
||||
|
||||
When PNG_DEBUG > 0, the following functions (macros) become available:
|
||||
|
||||
png_debug(level, message)
|
||||
png_debug1(level, message, p1)
|
||||
png_debug2(level, message, p1, p2)
|
||||
|
||||
in which "level" is compared to PNG_DEBUG to decide whether to print
|
||||
the message, "message" is the formatted string to be printed,
|
||||
and p1 and p2 are parameters that are to be embedded in the string
|
||||
according to printf-style formatting directives. For example,
|
||||
|
||||
png_debug1(2, "foo=%d\n", foo);
|
||||
|
||||
is expanded to
|
||||
|
||||
if(PNG_DEBUG > 2)
|
||||
fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
|
||||
|
||||
When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
|
||||
can still use PNG_DEBUG to control your own debugging:
|
||||
|
||||
#ifdef PNG_DEBUG
|
||||
fprintf(stderr, ...
|
||||
#endif
|
||||
|
||||
When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
|
||||
having level = 0 will be printed. There aren't any such statements in
|
||||
this version of libpng, but if you insert some they will be printed.
|
||||
|
||||
VI. Changes to Libpng from version 0.88
|
||||
|
||||
It should be noted that versions of libpng later than 0.96 are not
|
||||
distributed by the original libpng author, Guy Schalnat, nor by
|
||||
@ -1907,7 +2007,7 @@ allocating and freeing the png_struct for each image read.
|
||||
|
||||
Setting the error callbacks via png_set_message_fn() before
|
||||
png_read_init() as was suggested in libpng-0.88 is no longer supported
|
||||
because this caused applications which do not use custom error functions
|
||||
because this caused applications that do not use custom error functions
|
||||
to fail if the png_ptr was not initialized to zero. It is still possible
|
||||
to set the error callbacks AFTER png_read_init(), or to change them with
|
||||
png_set_error_fn(), which is essentially the same function, but with a
|
||||
|
@ -1,6 +1,6 @@
|
||||
.TH LIBPNGPF 3 "June 14, 1998"
|
||||
.TH LIBPNGPF 3 "December 29, 1998"
|
||||
.SH NAME
|
||||
libpng \- Portable Network Graphics (PNG) Reference Library 1.0.2 - June 14, 1998
|
||||
libpng \- Portable Network Graphics (PNG) Reference Library 1.0.2a - December 29, 1998
|
||||
(private functions)
|
||||
.SH SYNOPSIS
|
||||
#include <png.h>
|
||||
@ -88,7 +88,7 @@ row);
|
||||
|
||||
void png_do_read_transformations (png_structp png_ptr);
|
||||
|
||||
void png_do_rgb_to_gray (png_row_infop row_info, png_bytep
|
||||
int png_do_rgb_to_gray (png_row_infop row_info, png_bytep
|
||||
row);
|
||||
|
||||
void png_do_shift (png_row_infop row_info, png_bytep row,
|
||||
|
6
png.5
6
png.5
@ -1,4 +1,4 @@
|
||||
.TH PNG 5 "June 14, 1998"
|
||||
.TH PNG 5 "December 29, 1998"
|
||||
.SH NAME
|
||||
png \- Portable Network Graphics (PNG) format
|
||||
.SH DESCRIPTION
|
||||
@ -7,7 +7,7 @@ lossless, portable, well-compressed storage of raster images. PNG provides
|
||||
a patent-free replacement for GIF and can also replace many
|
||||
common uses of TIFF. Indexed-color, grayscale, and truecolor images are
|
||||
supported, plus an optional alpha channel. Sample depths range from
|
||||
1 to 16 bits.
|
||||
1 to 16 bits.
|
||||
.br
|
||||
|
||||
PNG is designed to work well in online viewing applications, such as the
|
||||
@ -15,7 +15,7 @@ World Wide Web, so it is fully streamable with a progressive display
|
||||
option. PNG is robust, providing both full file integrity checking and
|
||||
fast, simple detection of common transmission errors. Also, PNG can store
|
||||
gamma and chromaticity data for improved color matching on heterogeneous
|
||||
platforms.
|
||||
platforms.
|
||||
|
||||
.SH "SEE ALSO"
|
||||
.IR libpng(3), zlib(3), deflate(5), and zlib(5)
|
||||
|
21
png.c
21
png.c
@ -1,11 +1,11 @@
|
||||
|
||||
/* png.c - location for general purpose libpng functions
|
||||
*
|
||||
* libpng 1.0.2 - June 14, 1998
|
||||
* For conditions of distribution and use, see copyright notice in png.h
|
||||
* libpng version 1.0.2a - December 29, 1998
|
||||
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
|
||||
* Copyright (c) 1996, 1997 Andreas Dilger
|
||||
* Copyright (c) 1998, Glenn Randers-Pehrson
|
||||
*
|
||||
*/
|
||||
|
||||
#define PNG_INTERNAL
|
||||
@ -15,7 +15,8 @@
|
||||
/* Version information for C files. This had better match the version
|
||||
* string defined in png.h.
|
||||
*/
|
||||
char png_libpng_ver[12] = "1.0.2";
|
||||
|
||||
char png_libpng_ver[12] = "1.0.2a";
|
||||
|
||||
/* Place to hold the signature string for a PNG file. */
|
||||
png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
|
||||
@ -317,8 +318,8 @@ png_charp
|
||||
png_convert_to_rfc1123(png_structp png_ptr, png_timep ptime)
|
||||
{
|
||||
static PNG_CONST char short_months[12][4] =
|
||||
{"Jan", "Feb", "Mar", "Apr", "May", "Jun",
|
||||
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
|
||||
{"Jan", "Feb", "Mar", "Apr", "May", "Jun",
|
||||
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
|
||||
|
||||
if (png_ptr->time_buffer == NULL)
|
||||
{
|
||||
@ -345,3 +346,13 @@ png_convert_to_rfc1123(png_structp png_ptr, png_timep ptime)
|
||||
return ((png_charp)png_ptr->time_buffer);
|
||||
}
|
||||
#endif /* PNG_TIME_RFC1123_SUPPORTED */
|
||||
|
||||
png_charp
|
||||
png_get_copyright(png_structp png_ptr)
|
||||
{
|
||||
return("\n libpng version 1.0.2a - December 29, 1998\n\
|
||||
Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.\n\
|
||||
Copyright (c) 1996, 1997 Andreas Dilger\n\
|
||||
Copyright (c) 1998, Glenn Randers-Pehrson\n");
|
||||
}
|
||||
|
||||
|
117
png.h
117
png.h
@ -1,11 +1,10 @@
|
||||
|
||||
/* png.h - header file for PNG reference library
|
||||
*
|
||||
* libpng 1.0.2 - June 14, 1998
|
||||
* For conditions of distribution and use, see the COPYRIGHT NOTICE below.
|
||||
* libpng version 1.0.2a - December 29, 1998
|
||||
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
|
||||
* Copyright (c) 1996, 1997 Andreas Dilger
|
||||
* Copyright (c) 1998 Glenn Randers-Pehrson
|
||||
* Copyright (c) 1998, Glenn Randers-Pehrson
|
||||
*
|
||||
* Note about libpng version numbers:
|
||||
*
|
||||
@ -31,6 +30,9 @@
|
||||
* 1.0.0 1.0.0 100 2.1.0 [int should be 10000]
|
||||
* 1.0.1 1.0.1 10001 2.1.0
|
||||
* 1.0.1a-e 1.0.1a-e 10002 2.1.0.1a-e
|
||||
* 1.0.2 1.0.2 10002 2.1.0.2
|
||||
* 1.0.2a 1.0.2a 10003 2.1.0.2a
|
||||
* 1.0.3 1.0.3 10003 2.1.0.3
|
||||
*
|
||||
* Henceforth the source version will match the shared-library minor
|
||||
* and patch numbers; the shared-library major version number will be
|
||||
@ -117,14 +119,14 @@ extern "C" {
|
||||
*/
|
||||
|
||||
/* Version information for png.h - this should match the version in png.c */
|
||||
#define PNG_LIBPNG_VER_STRING "1.0.2"
|
||||
#define PNG_LIBPNG_VER_STRING "1.0.2a"
|
||||
|
||||
/* Careful here. At one time, Guy wanted to use 082, but that would be octal.
|
||||
* We must not include leading zeros.
|
||||
* Versions 0.7 through 1.0.0 were in the range 0 to 100 here (only
|
||||
* version 1.0.0 was mis-numbered 100 instead of 10000). From
|
||||
* version 1.0.1 it's xxyyzz, where x=major, y=minor, z=bugfix */
|
||||
#define PNG_LIBPNG_VER 10002 /* 1.0.2 */
|
||||
#define PNG_LIBPNG_VER 10003 /* 1.0.3 */
|
||||
|
||||
/* variables declared in png.c - only it needs to define PNG_NO_EXTERN */
|
||||