- From: Lea Verou via GitHub <sysbot+gh@w3.org>
- Date: Thu, 04 Apr 2024 21:24:40 +0000
- To: public-css-archive@w3.org
@jyasskin > I had trouble finding the tests for what's currently in the spec. First, I think we *all* have consensus that what is currently in the spec needs to be replaced, there have been several GMAs designed since that balance tradeoffs much better. > [w3.org/TR/css-color-4/#css-gamut-mapping](https://www.w3.org/TR/css-color-4/#css-gamut-mapping) just says "Used values of color are not exposed to script, making this hard to test in an automated manner." Yes, in an automated matter. But something like "minimize the perceptual difference between the specified and displayed color while preserving hue" is not testable *at all*. That said, I think we should actually discuss whether exposing the screen gamut is enough of a fingerprinting vector that we don't want to expose it. I personally don't think so but others may disagree. > Given a way to measure the output, I think one could test this with a rule that "the output color has to have a ΔΕ < X from the in-gamut color of the same hue as the target color with the least ΔΕ from the target color." Yup, that is pretty much exactly what I proposed and Chris C rejected 😀 Note that the guardrail cannot be in terms of ΔΕ, since that takes chroma into account as well, so a color with ΔΕ < X may not **exist**. But we can have guardrails for ΔL and ΔH, since a color that fits within those constraints is guaranteed to exist, even in the strictest form where ΔL = ΔH = 0 (you just lose a lot of chroma). If we want to frame it around ΔΕ, the X would need to somehow depend on the chroma difference between the colors, it cannot be a static number. > I'm trying to figure this out too, and in particular, what would go wrong if it's not the default. That said, if CSS does wind up preferring a "minimize the ΔΕ from the specified color" goal, that matches what @ccameron-chromium has said he can accept for images, so maybe we can actually have a compatible default. Can we make the goals for images a bit more concrete? Is preserving hue the main point of contentment? That people here want to prioritize preserving lightness and @ccameron-chromium wants to prioritize preserving hue? Because if so, we *can* have our cake and eat it too! We'd just specify low thresholds (or even 0) for *both* 😁 Again, as I have said many times in this thread, give us an exact set of requirements and we can come up with a spec/GMA that matches them. But there has been a lot of pushback by [Chris C] and no actual concrete requirements. In the most recent breakout, my takeaway about [Chris C]’s position was that he wants to just not gamut map. > I'm hopeful that the "prefer" in his March 5 answer, and his more recent March 27 statement that "... and we'd go implement it!" indicates some room to compromise. Links to comments would be appreciated since this is a long thread and expanding it all to search by date is very slow. > I should add that finding a compromise with Chromium isn't sufficient. We also need WebKit (@smfr?) and Gecko (@emilio?) to agree. It would definitely be good to hear from other vendors, though given the lack of pushback on their side, I suspect once we reach a compromise with Chromium they would be happy to follow (WebKit had even implemented an earlier version of the CSS GMA). -- GitHub Notification of comment by LeaVerou Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/9449#issuecomment-2038252398 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Thursday, 4 April 2024 21:24:40 UTC