59 lines
2.2 KiB
Plaintext
59 lines
2.2 KiB
Plaintext
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Known bugs and suggested enhancements in libpng-1.0.4
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1. March 15, 1998 -- OPTIMIZATION -- Kevin Bracey
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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-1.0.5. About 160 loops will be turned around
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in libpng-1.0.Nn, for testing.
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2. July 4, 1998 -- ENHANCEMENT -- Glenn R-P
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libpng-1.0.5 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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3. September 1999 -- ENHANCEMENT --
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It should be possible to use libpng without floating-point aritmetic.
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STATUS: Under investigation, implementation postponed until after
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libpng-1.0.5. The application interface will change because replacements
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for the png_set_gAMA(), png_set_cHRM(), and corresponding png_get_()
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functions will be needed.
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4. September 1999 -- BUG [FIXED] --
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Portions of the new MMX code in pngvcrd.c were ifdef'd out because they
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didn't work properly, but the bug appears to have been found and fixed.
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As a result, all parts of the code are once again enabled. If you think
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there's still a problem, you can recompile with one of the following two
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macros defined and see if the problem goes away:
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DISABLE_PNGVCRD_COMBINE
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DISABLE_PNGVCRD_INTERLACE
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The second one is in the function where the bug was; as far as we are
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aware, there was never any bug in the other function. Please notify us
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if you find any problems in libpng, regardless of whether the two macros
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make any difference: png-implement@ccrc.wustl.edu
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Again, we believe the MMX code in pngvcrd.c is 100% correct, but it has
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not yet been tested extensively.
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