
# YIQ: used by composite video signals (linear combinations of RGB)
# Y: perceived grey level (0.0 == black, 1.0 == white)
# I, Q: color components
  
def rgb_to_yiq(r, g, b):
    y = 0.30*r + 0.59*g + 0.11*b
    i = 0.60*r - 0.28*g - 0.32*b
    q = 0.21*r - 0.52*g + 0.31*b
    return (y, i, q)

def yiq_to_rgb(y, i, q):
    r = y + 0.948262*i + 0.624013*q
    g = y - 0.276066*i - 0.639810*q
    b = y - 1.105450*i + 1.729860*q

