- From: Chris Lilley via GitHub <sysbot+gh@w3.org>
- Date: Mon, 03 Mar 2025 19:41:53 +0000
- To: public-css-archive@w3.org
I think I see the problem. The spec [defines headroom](https://drafts.csswg.org/css-color-hdr-1/#defining-dynamic-range) in stops above reference white, so SDR is headroom `0` and HDR with three stops of headroom is `3`.. The original proposal uses a linear scale, so SDR has a headroom of `1` and HDR with three stops of headroom is `8`. This is also why **Interpolating colors based on headroom** takes the log of each headroom value, rather than using it directly. The ISO definition of headroom also uses the log value.  Consistently using the logarithmic value (ie in stops) has the following advantages: - an SDR system, with **no** headroom (reference white is peak white) has `H` of `0`, not `1` - the headroom values are evenly spaced, perceptually - the calculations are simplified, because there is no need to log the headroom values -- GitHub Notification of comment by svgeesus Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/11786#issuecomment-2695375888 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Monday, 3 March 2025 19:41:54 UTC