CIE XYZ CIE LAB Conversion

labxyz.c

vector xyzToLab(vector xyz) {
    float vx = xyz[0] / 0.95047;
    float vy = xyz[1];
    float vz = xyz[2] / 1.08883;

    vx = select(7.787 * vx + 16.0 / 116.0, pow(vx, 1.0 / 3.0), vx > 0.008856);
    vy = select(7.787 * vy + 16.0 / 116.0, pow(vy, 1.0 / 3.0), vy > 0.008856);
    vz = select(7.787 * vz + 16.0 / 116.0, pow(vz, 1.0 / 3.0), vz > 0.008856);

    return vector(
        116.0 * vy - 16.0,
        500.0 * (vx - vy),
        200.0 * (vy - vz));
}

vector labToXyz(vector lab) {
    float vy = (lab[0] + 16.0) / 116.0;
    float vx = lab[1] / 500.0 + vy;
    float vz = vy - lab[2] / 200.0;

    float vye3 = vy * vy * vy;
    float vxe3 = vx * vx * vx;
    float vze3 = vz * vz * vz;

    vy = select((vy - 16.0 / 116.0) / 7.787, vye3, vye3 > 0.008856);
    vx = select((vx - 16.0 / 116.0) / 7.787, vxe3, vxe3 > 0.008856);
    vz = select((vz - 16.0 / 116.0) / 7.787, vze3, vze3 > 0.008856);

    return vector(vx * 0.95047, vy, vz * 1.08883);
}