def lux(r, g, b):
    """Convert 8-bit RGB color to Lux.

    Arguments:
        r: Red value in the range 0-255.
        g: Green value in the range 0-255.
        b: Blue value in the range 0-255.

    Returns:
        Illuminance in Lux.
    """
    # Again, the constants are multiplied by 257.
    illuminance = (-83.43762 * r) + (405.64109 * g) + (-188.10087 * b)
    return abs(round(illuminance))