- From: Philip Jägenstedt via GitHub <sysbot+gh@w3.org>
- Date: Tue, 12 Mar 2024 21:31:08 +0000
- To: public-css-archive@w3.org
Thank you @bottosson! Quoting what I think are the most important bits. First @bottosson said: > I unfortunately didn't spend that much time calculating and validating that scaling factor when I first derived Oklab since I was mostly focused on the orthogonality between L, C and h (and I didn't expect it to become so widespread so quickly), and it seems like it is off by quite a bit. > > I've recently done some tests with color distance datasets as implemented in [Colorio](https://github.com/nschloe/colorio) and on both the [Combvd dataset](https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-25-7-1828) and the [OSA-UCS dataset](https://www.osapublishing.org/josa/abstract.cfm?uri=josa-64-12-1691) a scale factor of slightly more than 2 for a and b would give the best results (2.016 works best for Combvd and 2.045 for the OSA-UCS dataset). Then @svgeesus said: > - scaling OKLab a & b relative to L solely based on deltaE 2000 comparisons on the neutral axis picks the point of maximum CIELAB a & b asymmetry > - scaling based on some dataset of color pairs will depend on the distribution of mean chroma in that data set Finally @bottosson said: > Small scale color distances show very strong elongation of spheres into ellipses: >  > > [...] > > It is also possible to much closer match the small color difference dataset as well, by introducing chroma compression, similar to what both CIEDE2000 and Ciecam02/16-UCS do, but that also adds quite a bit of complexity and assumptions on viewing conditions, this performs worse for tasks such as color interpolation The discussion was in the context of changing Oklab, and that's no longer possible. For computing color distance, however, what's the takeaway from this? Is the "right" scale definitely something close to 2, or is "chroma compression" necessary to avoid the "very strong elongation of spheres into ellipses"? -- GitHub Notification of comment by foolip Please view or discuss this issue at https://github.com/w3c/csswg-drafts/pull/10063#issuecomment-1992621279 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Tuesday, 12 March 2024 21:31:09 UTC