Luv

import { registerColorFunction } from "saturon/utils";

/**
 * @see {@link http://www.brucelindbloom.com/index.html?Eqn_Luv_to_XYZ.html|Luv to XYZ}
 * @see {@link http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_Luv.html|XYZ to Luv}
 */
registerColorFunction("luv", {
    components: {
        l: { index: 0, value: "percentage", precision: 5 },
        u: { index: 1, value: [-100, 100], precision: 5 },
        v: { index: 2, value: [-100, 100], precision: 5 },
    },
    targetGamut: null,
    bridge: "xyz-d50",
    toBridge: ([L, u, v]: number[]) => {
        const Xn = 0.96422;
        const Yn = 1.0;
        const Zn = 0.82521;
        if (L === 0) return [0, 0, 0];
        const denom_n = Xn + 15 * Yn + 3 * Zn;
        const u_n = (4 * Xn) / denom_n;
        const v_n = (9 * Yn) / denom_n;
        const Y = L > 8 ? Yn * Math.pow((L + 16) / 116, 3) : Yn * (L / 903.3);
        const u_prime = u / (13 * L) + u_n;
        const v_prime = v / (13 * L) + v_n;
        const X = (9 * Y * u_prime) / (4 * v_prime);
        const Z = (Y * (12 - 3 * u_prime - 20 * v_prime)) / (4 * v_prime);
        return [X, Y, Z];
    },
    fromBridge: ([X, Y, Z]: number[]) => {
        const Xn = 0.96422;
        const Yn = 1.0;
        const Zn = 0.82521;
        const denom_n = Xn + 15 * Yn + 3 * Zn;
        const u_n = (4 * Xn) / denom_n;
        const v_n = (9 * Yn) / denom_n;
        const denom = X + 15 * Y + 3 * Z;
        const u_prime = denom !== 0 ? (4 * X) / denom : 0;
        const v_prime = denom !== 0 ? (9 * Y) / denom : 0;
        const Yr = Y / Yn;
        const L = Yr > Math.pow(6 / 29, 3) ? 116 * Math.cbrt(Yr) - 16 : 903.3 * Yr;
        if (L === 0) return [0, 0, 0];
        const u = 13 * L * (u_prime - u_n);
        const v = 13 * L * (v_prime - v_n);
        return [L, u, v];
    },
});