- From: L. David Baron via GitHub <noreply@w3.org>
- Date: Fri, 27 Jun 2025 15:01:54 +0000
- To: public-fxtf-archive@w3.org
> I think the formula should be this: > > co = max(0, Cb - (1 - Cs) * αs) = max(0, Cb + Cs * αs - αs); αo = min(1, αs + αb); > > This fits perfectly with what I see in Figma. Based on testing Safari with editing the above into https://wpt.live/css/compositing/canvas-composite-modes.html that doesn't appear to work, at the very least because it doesn't produce proper premultiplied results. The first error is: > assert_equals: premultiplication zero check: g=0 a=0 plus-darker g=47 a=0 expected 0 but got 0.1843137254901961 which indicates that it's producing a color output larger than the alpha output, which is not valid for something that is expected to produce premultiplied outputs. It also seems wrong because it doesn't treat source and destination the same, whereas the other formulas for `plus-lighter` and `plus-darker` do not change if you swap source and destination. -- GitHub Notification of comment by dbaron Please view or discuss this issue at https://github.com/w3c/fxtf-drafts/issues/447#issuecomment-3013378414 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Friday, 27 June 2025 15:01:55 UTC