[fxtf-drafts] [compositing-2] 'lighter' vs 'plus-lighter' (#446)

jakearchibald has just created a new issue for https://github.com/w3c/fxtf-drafts:

== [compositing-2] 'lighter' vs 'plus-lighter' ==
https://drafts.fxtf.org/compositing/#porterduffcompositingoperators_plus_lighter

The difference between `lighter` and `plus-lighter` is that `plus-lighter` caps to 1. However, I can't find any cases where `lighter` allows values to go above 1. Here's a couple of canvases that I'd expect to be different if values were allowed to go above 1 https://static-misc-3.glitch.me/composite-test/cap.html - in this case both the red channel and alpha channel would go above 1.

`plus-lighter` and `plus-darker` were added when the compositing-2 doc was added https://github.com/w3c/fxtf-drafts/commit/10f0d3dfd827022f156d033e3d9ac4f9f3ca05ef. I can't find any discussion of these, but I guess there must have been. @cabanier, @dbaron do either of you know the history here?

I wonder if it would make sense to specify that all blend and compositing modes are clamped to 0-1. Then, remove `plus-lighter` from the spec, and rename `plus-darker` to `darker` and remove the clamping (since it'd be covered by the overall clamping.

Please view or discuss this issue at https://github.com/w3c/fxtf-drafts/issues/446 using your GitHub account


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Received on Monday, 29 November 2021 11:09:51 UTC