[cairo] compositing choices

Tiberiu Tesileanu legendre17 at hotmail.com
Fri May 28 10:42:16 PDT 2010


I was wondering whether there is a way to change the way in which Cairo blends colors currently in the buffer with the ones being painted over.  The default is alpha blending, but sometimes different choices are useful.  For example, if I wanted to simulate lens flare or double exposure of pictures, or motion blur, I would need a blending mode in which the R, G, B components are added between source and background, as opposed to using a weighted average as in alpha blending.  Or if I wanted to simulate painting, I would need some subtractive blending of colors.  Is there way a to achieve this kind of effects in Cairo?

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