Support "plus-darker" in mix-blend mode

• Component: CSS
• Status: RESOLVED FIXED

[Dean Jackson]

Support for "plus-darker" in mix-blend-mode. Here is the email I sent to public-fx.

https://lists.w3.org/Archives/Public/public-fx/2015JanMar/0021.html

Our designers at Apple often request a blending operation that is not supported in the CSS Compositing and Blending specification: plus-darker. You can find many examples and discussion of this mode if you Bing on the Google.

We’d like to add this mode to Level 2.

Details are here: http://en.wikipedia.org/wiki/Blend_modes#Addition

The math is pretty simple:

R = min(0, (1 - D) + (1 - S))

(We should maybe consider adding plus-lighter as well, and subtractive modes based on designer feedback)

[Dean Jackson]

rdar://problem/19523370

[Dean Jackson]

Created attachment 244946 [details]
Patch

[Dean Jackson]

Committed r178710: <http://trac.webkit.org/changeset/178710>