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

Imported from libpng-1.0.9beta6.tar

Browse Source
This commit is contained in:
Glenn Randers-Pehrson
2000-12-18 09:33:57 -06:00
parent 2ad31ae31f
commit 408b421265
48 changed files with 231 additions and 121 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
libpng.txt
View File

@@ -1,6 +1,6 @@
libpng.txt - A description on how to use and modify libpng
libpng version 1.0.9beta5 - December 15, 2000
libpng version 1.0.9beta6 - December 18, 2000
Updated and distributed by Glenn Randers-Pehrson
<randeg@alum.rpi.edu>
Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson
@@ -400,7 +400,7 @@ in until png_read_end() has read the chunk data following the image.
png_get_IHDR(png_ptr, info_ptr, &width, &height,
&bit_depth, &color_type, &interlace_type,
&compression_type, &filter_type);
&compression_type, &filter_method);
width - holds the width of the image
in pixels (up to 2^31).
@@ -428,15 +428,18 @@ in until png_read_end() has read the chunk data following the image.
PNG_COLOR_MASK_COLOR
PNG_COLOR_MASK_ALPHA
filter_type - (must be PNG_FILTER_TYPE_BASE
for PNG 1.0)
filter_method - (must be PNG_FILTER_TYPE_BASE
for PNG 1.0, and can also be
PNG_INTRAPIXEL_DIFFERENCING if
the PNG datastream is embedded in
a MNG-1.0 datastream)
compression_type - (must be PNG_COMPRESSION_TYPE_BASE
for PNG 1.0)
interlace_type - (PNG_INTERLACE_NONE or
PNG_INTERLACE_ADAM7)
Any or all of interlace_type, compression_type, of
filter_type can be NULL if you are not
interested in their values.
filter_method can be NULL if you are
not interested in their values.
channels = png_get_channels(png_ptr, info_ptr);
channels - number of channels of info for the
@@ -466,7 +469,7 @@ in until png_read_end() has read the chunk data following the image.
info_ptr);
color_type = png_get_color_type(png_ptr,
info_ptr);
filter_type = png_get_filter_type(png_ptr,
filter_method = png_get_filter_type(png_ptr,
info_ptr);
compression_type = png_get_compression_type(png_ptr,
info_ptr);
@@ -1539,10 +1542,11 @@ maximum possible compression at the expense of slower writing. If you
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
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 PNG specification for details on the specific filter
the filter method, for which the only valid values are 0 (as of the
July 1999 PNG specification, version 1.2) or 64 (if you are writing
a PNG datastream that is to be embedded in a MNG datastream). The third
parameter is a flag that indicates which filter type(s) are to be tested
for each scanline. See the PNG specification for details on the specific filter
types.
@@ -1563,6 +1567,9 @@ it should start out with all of the filters (to ensure that the previous
row of pixels will be stored in case it's needed later), and then add
and remove them after the start of compression.
If you are writing a PNG datastream that is to be embedded in a MNG
datastream, the second parameter can be either 0 or 64.
The png_set_compression_*() functions interface to the zlib compression
library, and should mostly be ignored unless you really know what you are
doing. The only generally useful call is png_set_compression_level()
@@ -1601,7 +1608,7 @@ Some of the more important parts of the png_info are:
png_set_IHDR(png_ptr, info_ptr, width, height,
bit_depth, color_type, interlace_type,
compression_type, filter_type)
compression_type, filter_method)
width - holds the width of the image
in pixels (up to 2^31).
height - holds the height of the image
@@ -1633,7 +1640,11 @@ Some of the more important parts of the png_info are:
PNG_INTERLACE_ADAM7
compression_type - (must be
PNG_COMPRESSION_TYPE_DEFAULT)
filter_type - (must be PNG_FILTER_TYPE_DEFAULT)
filter_method - (must be PNG_FILTER_TYPE_DEFAULT
or, if you are writing a PNG to
be embedded in a MNG datastream,
can also be
PNG_INTRAPIXEL_DIFFERENCING)
png_set_PLTE(png_ptr, info_ptr, palette,
num_palette);
@@ -2470,6 +2481,10 @@ structures appropriately for all of the filter types.
png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
filters);
The second parameter can also be PNG_INTRAPIXEL_DIFFERENCING
if you are writing a PNG to be embedded in a MNG
datastream. This parameter must be the same as the
value of filter_method used in png_set_IHDR().
It is also possible to influence how libpng chooses from among the
available filters. This is done in two ways - by telling it how
@@ -2598,6 +2613,11 @@ png_permit_mng_features() function:
your mask with the set of MNG features that is
supported by the version of libpng that you are using.
It is an error to use this function when reading or writing a standalone
PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
in a MNG datastream (as a minimum, it must have the MNG 8-byte signature
and the MHDR and MEND chunks).
VII. Changes to Libpng from version 0.88
It should be noted that versions of libpng later than 0.96 are not
@@ -2649,13 +2669,13 @@ application:
VIII. Y2K Compliance in libpng
December 15, 2000
December 18, 2000
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 0.71 and
upward through 1.0.9beta5 are Y2K compliant. It is my belief that earlier
upward through 1.0.9beta6 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