Update of bug #20157 (project mypaint):
Status: None => In Progress
Assigned to: None => achadwick
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Follow-up Comment #1:
Overlay and hard-light done,
https://gitorious.org/mypaint/mypaint/commit/e7b6510109e8a69b15f4fab4bbe8fc981b90665f
https://gitorious.org/mypaint/mypaint/commit/b7273e01e3843004b5557880ef8249518a3b6bad
and tested against the W3C examples
http://www.w3.org/TR/SVGCompositing/#comp-op-overlay
http://www.w3.org/TR/SVGCompositing/#comp-op-hard-light
They look identical if you save from MyPaint as transparent PNG and then
display them over a grey-chequer background in something like ristretto or eog
:)
Soft light is trickier due to the complexity of the W3C equation and having
working in our somewhat odd scaled int representation. In other words, not
quite there yet, but working on it.
http://www.w3.org/TR/SVGCompositing/#comp-op-soft-light
It requires a good sqrt() approximation for scaled ints. The Babylonian method
with a lookup table of 16 or so starting guesses looks fast enough (avg ~1.977
iterations, max 8 in the range we use) and quite light on space. If we need it
to go faster, we can use a full 15-bit LUT...
I don't think MyPaint should be bug-for-bug compatible with the GIMP.
Soft-light is a different blend mode from overlay.
(file #16723, file #16724)
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Additional Item Attachment:
File name: overlay.ora Size:210 KB
File name: hard-light.ora Size:220 KB
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