- From: Chris Lilley via GitHub <sysbot+gh@w3.org>
- Date: Tue, 05 Jul 2022 13:53:06 +0000
- To: public-css-archive@w3.org
```js
const JND = 0.02;
const ε = 0.0001;
function gamutMap (origin, destination) {
// OKLCH is the CSS GMA working space
let origin_OKLCH = to(origin, 'oklch');
let L = origin_OKLCH.coords[0];
// return media white or black, if lightness is out of range
if (L >= 1) return {space: destination, coords: [1, 1, 1], alpha: origin.alpha};
if (L <= 0) return {space: destination, coords: [0, 0, 0], alpha: origin.alpha};
// otherwise, return origin in destination, if in gamut
if (inGamut(origin, destination)) return to(origin, destination);
// set up for OKLCH chroma reduction
let min = 0;
let max = origin_OKLCH.coords[1];
let min_inGamut = true;
let current = clone(origin_OKLCH);
let clipped = clip(current, destination);
// but first check if we are "close" to in gamut
let E = deltaEOK(clipped, current);
if (E < JND) return clipped;
// now actually binary search for the in-gamut chroma value
// console.log("pre-checks complete, still here, doing actual gamut mapping");
while (max - min > ε) {
let chroma = (min + max) / 2;
current.coords[1] = chroma;
if (min_inGamut && inGamut(current, destination)) {
min = chroma
} else {
clipped = clip(current, destination);
E = deltaEOK(clipped, current);
if (E < JND) {
if (JND - E < ε) {
return clipped;
} else {
min_inGamut = false;
min = chroma
}
} else {
max = chroma;
}
}
} // end of chroma reduction loop
return current;
}
```
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Received on Tuesday, 5 July 2022 13:53:08 UTC