- From: L. David Baron via GitHub <sysbot+gh@w3.org>
- Date: Wed, 30 Aug 2023 14:27:54 +0000
- To: public-fxtf-archive@w3.org
I wrote a test in https://github.com/web-platform-tests/wpt/pull/41713 that tests the composite modes in canvas. It turns out my test objected to the formula in https://github.com/w3c/fxtf-drafts/issues/447#issuecomment-1489513453 because it wasn't producing properly premultiplied colors: there were cases where the color result was greater than the alpha result, which isn't allowed. However, my formula was sort of close; it appears (based on fiddling with my test) that what Safari implements for `plus-darker` is: co = min(1, αs + αb) - min(1, αs x (1 - Cs) + αb x (1 - Cb)); αo = min(1, αs + αb); (It's possible there's a simpler way to write this, but that's the expression I figured out that leads to Safari passing the test for `plus-darker`.) -- GitHub Notification of comment by dbaron Please view or discuss this issue at https://github.com/w3c/fxtf-drafts/issues/447#issuecomment-1699293766 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Wednesday, 30 August 2023 14:27:56 UTC