[master] Updated documentation
Merged libpng-1.2.41.txt with libpng-1.4.0.txt where appropriate.
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Glenn Randers-Pehrson
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1
ANNOUNCE
1
ANNOUNCE
@ -89,6 +89,7 @@ version 1.2.41beta09 [November 1, 2009]
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More bugfixes and improvements to CMakeLists.txt (Philip Lowman)
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Moved CMakeLists.txt from scripts into the main libpng directory.
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Apply png_user_chunk_cache_max within png_decompress_chunk().
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Merged libpng-1.2.41.txt with libpng-1.4.0.txt where appropriate.
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Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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1
CHANGES
1
CHANGES
@ -2519,6 +2519,7 @@ version 1.2.41beta09 [November 1, 2009]
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More bugfixes and improvements to CMakeLists.txt (Philip Lowman)
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Moved CMakeLists.txt from scripts into the main libpng directory.
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Apply png_user_chunk_cache_max within png_decompress_chunk().
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Merged libpng-1.2.41.txt with libpng-1.4.0.txt where appropriate.
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Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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(subscription required; visit
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@ -1,6 +1,6 @@
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libpng.txt - A description on how to use and modify libpng
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libpng version 1.2.41beta09 - October 30, 2009
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libpng version 1.2.41beta09 - November 1, 2009
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Updated and distributed by Glenn Randers-Pehrson
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<glennrp at users.sourceforge.net>
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Copyright (c) 1998-2009 Glenn Randers-Pehrson
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@ -11,7 +11,7 @@ libpng.txt - A description on how to use and modify libpng
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Based on:
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libpng versions 0.97, January 1998, through 1.2.41beta09 - October 30, 2009
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libpng versions 0.97, January 1998, through 1.2.41beta09 - November 1, 2009
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Updated and distributed by Glenn Randers-Pehrson
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Copyright (c) 1998-2009 Glenn Randers-Pehrson
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@ -410,6 +410,19 @@ If you need to retrieve the limits that are being applied, use
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width_max = png_get_user_width_max(png_ptr);
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height_max = png_get_user_height_max(png_ptr);
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The PNG specification sets no limit on the number of ancillary chunks
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allowed in a PNG datastream. You can impose a limit on the total number
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of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with
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png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
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where 0x7fffffffL means unlimited. You can retrieve this limit with
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chunk_cache_max = png_get_chunk_cache_max(png_ptr);
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This limit also applies to the number of buffers that can be allocated
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by png_decompress_chunk().
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The high-level read interface
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At this point there are two ways to proceed; through the high-level
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@ -437,6 +450,8 @@ you want to do are limited to the following set:
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PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
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to transparency
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PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
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PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples
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to RGB (or GA to RGBA)
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(This excludes setting a background color, doing gamma transformation,
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dithering, and setting filler.) If this is the case, simply do this:
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@ -680,6 +695,10 @@ into the info_ptr is returned for any complex types.
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string for unknown).
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text_ptr[i].lang_key - keyword in UTF-8
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(empty string for unknown).
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Note that the itxt_length, lang, and lang_key
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members of the text_ptr structure only exist
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when the library is built with iTXt chunk support.
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num_text - number of comments (same as
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num_comments; you can put NULL here
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to avoid the duplication)
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@ -859,6 +878,43 @@ things.
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As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
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added. It expands the sample depth without changing tRNS to alpha.
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As of libpng version 1.2.41beta09, not all possible expansions are supported.
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In the following table, the 01 means grayscale with depth<8, 31 means
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indexed with depth<8, other numerals represent the color type, "T" means
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the tRNS chunk is present, A means an alpha channel is present, and O
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means tRNS or alpha is present but all pixels in the image are opaque.
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FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O
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TO
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01 -
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31 -
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0 1 -
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0T -
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0O -
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2 GX -
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2T -
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2O -
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3 1 -
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3T -
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3O -
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4A T -
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4O -
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6A GX TX TX -
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6O GX TX -
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Within the matrix,
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"-" means the transformation is not supported.
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"X" means the transformation is obtained by png_set_expand().
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"1" means the transformation is obtained by
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png_set_expand_gray_1_2_4_to_8
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"G" means the transformation is obtained by
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png_set_gray_to_rgb().
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"P" means the transformation is obtained by
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png_set_expand_palette_to_rgb().
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"T" means the transformation is obtained by
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png_set_tRNS_to_alpha().
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PNG can have files with 16 bits per channel. If you only can handle
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8 bits per channel, this will strip the pixels down to 8 bit.
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@ -1916,6 +1972,10 @@ width, height, bit_depth, and color_type must be the same in each call.
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empty for unknown).
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text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
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or empty for unknown).
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Note that the itxt_length, lang, and lang_key
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members of the text_ptr structure only exist
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when the library is built with iTXt chunk support.
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num_text - number of comments
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png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
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@ -3146,7 +3206,7 @@ source.
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XIII. Y2K Compliance in libpng
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October 30, 2009
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November 1, 2009
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Since the PNG Development group is an ad-hoc body, we can't make
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an official declaration.
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