import math


def uncompand(A):
    """ Uncompand an sRGB byte value to a linearized value """
    # q.v. http://www.brucelindbloom.com/index.html?Eqn_RGB_to_XYZ.html
    V = A / 255.0
    return (V <= 0.04045) and (V / 12.92) or math.pow(((V + 0.055) / 1.055), 2.4)