Script to convert RGB color to CIE color space

rgb2cie.py

import sys

def rgb_to_xy(r, g, b):
    X = 0.412453 * r + 0.357580 * g + 0.180423 * b
    Y = 0.212671 * r + 0.715160 * g + 0.072169 * b
    Z = 0.019334 * r + 0.119193 * g + 0.950227 * b
    x = X / (X+Y+Z)
    y = Y / (X+Y+Z)
    return x, y

if __name__ == '__main__':
    if len(sys.argv) != 4:
        print "Incorrect number of parameters.\nUsage: %s r g b" % sys.argv[0]
        sys.exit(1)
    r, g, b = map(float, sys.argv[1:4])
    print rgb_to_xy(r, g, b)