chroma-js/src/io/oklab/oklab2rgb.js

JavaScript library for color conversions

import { unpack } from '../../utils/index.js';
import multiplyMatrices from '../../utils/multiply-matrices.js';
import { xyz2rgb } from '../lab/lab2rgb.js';

const oklab2rgb = (...args) => {
    args = unpack(args, 'lab');
    const [L, a, b, ...rest] = args;
    const [X, Y, Z] = OKLab_to_XYZ([L, a, b]);
    const [r, g, b_] = xyz2rgb(X, Y, Z);
    return [r, g, b_, ...(rest.length > 0 && rest[0] < 1 ? [rest[0]] : [])];
};

// from https://www.w3.org/TR/css-color-4/#color-conversion-code
function OKLab_to_XYZ(OKLab) {
    // Given OKLab, convert to XYZ relative to D65
    var LMStoXYZ = [
        [1.2268798758459243, -0.5578149944602171, 0.2813910456659647],
        [-0.0405757452148008, 1.112286803280317, -0.0717110580655164],
        [-0.0763729366746601, -0.4214933324022432, 1.5869240198367816]
    ];
    var OKLabtoLMS = [
        [1.0, 0.3963377773761749, 0.2158037573099136],
        [1.0, -0.1055613458156586, -0.0638541728258133],
        [1.0, -0.0894841775298119, -1.2914855480194092]
    ];

    var LMSnl = multiplyMatrices(OKLabtoLMS, OKLab);
    return multiplyMatrices(
        LMStoXYZ,
        LMSnl.map((c) => c ** 3)
    );
}

export default oklab2rgb;