LAB_CONSTANTS =
    # Corresponds roughly to RGB brighter/darker
    Kn: 18

    # D65 standard referent
    Xn: 0.950470
    Yn: 1
    Zn: 1.088830

    t0: 0.137931034  # 4 / 29
    t1: 0.206896552  # 6 / 29
    t2: 0.12841855   # 3 * t1 * t1
    t3: 0.008856452  # t1 * t1 * t1