Hello everyone. First I would like to say that pygame is one of the best integrated Python packages I've seen so far; very slick. Anyway, down to business. While blitting from a surface with per-pixel alpha to a surface also with per-pixel alpha I found a bug when source alpha is 255. Each calculated color value is one less than that of the source. I have attached a program that illustrates the problem. I have also included a patch for alphablit.c in CVS which hopefully solves the problem. The C expression used is based on the formula: blend(s, sA, d) = ( (256 - sA)*d + (sA + 1)*s) / 256 I have checked the expression to confirm the following: blend(s, 0, d) = d blend(s, 255, d) = s blend(0, sA, 0) = 0 blend(255, sA, 255) = 255 blend(s, sA, d) <= 255 I am using pygame 1.7.1 with both Python 2.3 and 2.4 on Windows. Lenard Lindstrom <len-l@xxxxxxxxx>
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Date: 23 Apr 2006, 21:03
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Date: 24 Apr 2006, 16:37
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