https://colorjs.io/src/luminance.js

1/**
2 * Relative luminance
3 */
4import get from "./get.js";
5import set from "./set.js";
6import xyz_d65 from "./spaces/xyz-d65.js";
7
8/** @import { ColorTypes } from "./types.js" */
9
10/**
11 *
12 * @param {ColorTypes} color
13 * @returns {number}
14 */
15export function getLuminance (color) {
16	// Assume getColor() is called on color in get()
17	return get(color, [xyz_d65, "y"]);
18}
19
20/**
21 * @param {ColorTypes} color
22 * @param {number | ((coord: number) => number)} value
23 */
24export function setLuminance (color, value) {
25	// Assume getColor() is called on color in set()
26	set(color, [xyz_d65, "y"], value);
27}
28
29/**
30 * @param {typeof import("./color.js").default} Color
31 */
32export function register (Color) {
33	Object.defineProperty(Color.prototype, "luminance", {
34		get () {
35			return getLuminance(this);
36		},
37		set (value) {
38			setLuminance(this, value);
39		},
40	});
41}