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libpng.txt
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libpng.txt
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libpng.txt - A description on how to use and modify libpng
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libpng version 1.0.9beta7 - December 28, 2000
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libpng version 1.0.9beta8 - January 12, 2001
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Updated and distributed by Glenn Randers-Pehrson
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<randeg@alum.rpi.edu>
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Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson
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V. Modifying/Customizing libpng:
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There are two issues here. The first is changing how libpng does
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There are three issues here. The first is changing how libpng does
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standard things like memory allocation, input/output, and error handling.
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The second deals with more complicated things like adding new chunks,
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adding new transformations, and generally changing how libpng works.
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Both of those are compile-time issues; that is, they are generally
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determined at the time the code is written, and there is rarely a need
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to provide the user with a means of changing them. The third is a
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run-time issue: choosing between and/or tuning one or more alternate
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versions of computationally intensive routines; specifically, optimized
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assembly-language (and therefore compiler- and platform-dependent)
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versions.
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Memory allocation, input/output, and error handling
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All of the memory allocation, input/output, and error handling in libpng
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goes through callbacks that are user settable. The default routines are
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goes through callbacks that are user-settable. The default routines are
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in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
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these functions, call the appropriate png_set_*_fn() function.
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@@ -2596,6 +2605,7 @@ When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
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having level = 0 will be printed. There aren't any such statements in
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this version of libpng, but if you insert some they will be printed.
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VI. MNG support
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The MNG specification (available at http://www.libpng.org/pub/mng) allows
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VIII. Y2K Compliance in libpng
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December 28, 2000
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January 12, 2001
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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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This is your unofficial assurance that libpng from version 0.71 and
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upward through 1.0.9beta7 are Y2K compliant. It is my belief that earlier
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upward through 1.0.9beta8 are Y2K compliant. It is my belief that earlier
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versions were also Y2K compliant.
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Libpng only has three year fields. One is a 2-byte unsigned integer that
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