chroma-js/src/io/hsl/rgb2hsl.js

JavaScript library for color conversions

import { unpack, min, max } from '../../utils/index.js';

/*
 * supported arguments:
 * - rgb2hsl(r,g,b)
 * - rgb2hsl(r,g,b,a)
 * - rgb2hsl([r,g,b])
 * - rgb2hsl([r,g,b,a])
 * - rgb2hsl({r,g,b,a})
 */
const rgb2hsl = (...args) => {
    args = unpack(args, 'rgba');
    let [r, g, b] = args;

    r /= 255;
    g /= 255;
    b /= 255;

    const minRgb = min(r, g, b);
    const maxRgb = max(r, g, b);

    const l = (maxRgb + minRgb) / 2;
    let s, h;

    if (maxRgb === minRgb) {
        s = 0;
        h = Number.NaN;
    } else {
        s =
            l < 0.5
                ? (maxRgb - minRgb) / (maxRgb + minRgb)
                : (maxRgb - minRgb) / (2 - maxRgb - minRgb);
    }

    if (r == maxRgb) h = (g - b) / (maxRgb - minRgb);
    else if (g == maxRgb) h = 2 + (b - r) / (maxRgb - minRgb);
    else if (b == maxRgb) h = 4 + (r - g) / (maxRgb - minRgb);

    h *= 60;
    if (h < 0) h += 360;
    if (args.length > 3 && args[3] !== undefined) return [h, s, l, args[3]];
    return [h, s, l];
};

export default rgb2hsl;