ENH: Non-CG blend modes #7

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iccir opened this Issue Jan 1, 2012 · 0 comments

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iccir commented Jan 1, 2012

The following blend mode don't have direct mappings to CGBlendModes:
Layer, Add, Subtract, Invert, Alpha, Erase

Add is close to kCGBlendModePlusLighter, but handles the alpha channel differently.
Invert is close to kCGBlendModeDifference, but draws using all black.

Erase and Alpha may have equivalent Porter-Duff modes.

See:
http://www.kaourantin.net/2005/09/some-word-on-blend-modes-in-flash.html

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