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hsl.js
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hsl.js
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import ColorSpace from "../space.js";
import sRGB from "./srgb.js";
export default new ColorSpace({
id: "hsl",
name: "HSL",
coords: {
h: {
refRange: [0, 360],
type: "angle",
name: "Hue"
},
s: {
range: [0, 100],
name: "Saturation"
},
l: {
range: [0, 100],
name: "Lightness"
}
},
base: sRGB,
// Adapted from https://drafts.csswg.org/css-color-4/better-rgbToHsl.js
fromBase: rgb => {
let max = Math.max(...rgb);
let min = Math.min(...rgb);
let [r, g, b] = rgb;
let [h, s, l] = [NaN, 0, (min + max)/2];
let d = max - min;
if (d !== 0) {
s = (l === 0 || l === 1) ? 0 : (max - l) / Math.min(l, 1 - l);
switch (max) {
case r: h = (g - b) / d + (g < b ? 6 : 0); break;
case g: h = (b - r) / d + 2; break;
case b: h = (r - g) / d + 4;
}
h = h * 60;
}
// Very out of gamut colors can produce negative saturation
// If so, just rotate the hue by 180 and use a positive saturation
// see https://github.com/w3c/csswg-drafts/issues/9222
if (s < 0) {
h += 180;
s = Math.abs(s);
}
if (h >= 360) {
h -= 360;
}
return [h, s * 100, l * 100];
},
// Adapted from https://en.wikipedia.org/wiki/HSL_and_HSV#HSL_to_RGB_alternative
toBase: hsl => {
let [h, s, l] = hsl;
h = h % 360;
if (h < 0) {
h += 360;
}
s /= 100;
l /= 100;
function f (n) {
let k = (n + h/30) % 12;
let a = s * Math.min(l, 1 - l);
return l - a * Math.max(-1, Math.min(k - 3, 9 - k, 1));
}
return [f(0), f(8), f(4)];
},
formats: {
"hsl": {
coords: ["<number> | <angle>", "<percentage>", "<percentage>"],
},
"hsla": {
coords: ["<number> | <angle>", "<percentage>", "<percentage>"],
commas: true,
lastAlpha: true,
}
},
});