Bug 140646

Summary: Support "plus-darker" in mix-blend mode
Product: WebKit Reporter: Dean Jackson <dino>
Component: CSSAssignee: Dean Jackson <dino>
Status: RESOLVED FIXED    
Severity: Normal    
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
Patch simon.fraser: review+

Description Dean Jackson 2015-01-19 16:33:00 PST
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)
Comment 1 Dean Jackson 2015-01-19 16:33:12 PST
rdar://problem/19523370
Comment 2 Dean Jackson 2015-01-19 17:45:27 PST
Created attachment 244946 [details]
Patch
Comment 3 Dean Jackson 2015-01-20 08:04:06 PST
Committed r178710: <http://trac.webkit.org/changeset/178710>