luminance.py

def luminance(r,g,b):
    return math.sqrt(0.299 * math.pow(r,2) + 0.587 * math.pow(g,2) + 0.114 * math.pow(b,2))

def tint_to_lum(color, lum):
    r,g,b = color
    nR,nG,nB = r,g,b
    while True:
        tint_factor = .005

        nR = nR + (255 - nR) * tint_factor
        nG = nG + (255 - nG) * tint_factor
        nB = nB + (255 - nB) * tint_factor
        if luminance(nR,nG,nB)>=lum:
            break
    return int(nR), int(nG), int(nB)