三种彩色模型（RGB、CMY/CMYK、HSI）及其互相转换的全部代码

RGB转换为CMY/CMYK：

def rgb_to_cmy(rgb):
    cmy = [1 - val / 255 for val in rgb]
    return cmy

def rgb_to_cmyk(rgb):
    cmy = rgb_to_cmy(rgb)
    k = min(cmy)
    if k == 1:
        return [0, 0, 0, 1]
    cmyk = [(c - k) / (1 - k) for c in cmy]
    cmyk.append(k)
    return cmyk

CMY/CMYK转换为RGB：

def cmy_to_rgb(cmy):
    rgb = [int((1 - val) * 255) for val in cmy]
    return rgb

def cmyk_to_rgb(cmyk):
    cmy = [(c * (1 - k) + k) for c in cmyk[:3]]
    rgb = cmy_to_rgb(cmy)
    return rgb

RGB转换为HSI：

def rgb_to_hsi(rgb):
    r, g, b = rgb
    i = (r + g + b) / 3.0
    num = ((r - g) + (r - b)) / 2.0
    den = ((r - g) ** 2 + (r - b) * (g - b)) ** 0.5
    if den == 0:
        den = 0.01
    theta = math.acos(num / den)
    h = theta if b <= g else 2 * math.pi - theta
    s = 1 - 3 * min(rgb) / sum(rgb) if sum(rgb) != 0 else 0
    return [h, s, i]

HSI转换为RGB：

def hsi_to_rgb(hsi):
    h, s, i = hsi
    r, g, b = 0, 0, 0
    if h < 2 * math.pi / 3:
        b = i * (1 - s)
        r = i * (1 + s * math.cos(h) / math.cos(math.pi / 3 - h))
        g = 3 * i - (r + b)
    elif h < 4 * math.pi / 3:
        h -= 2 * math.pi / 3
        r = i * (1 - s)
        g = i * (1 + s * math.cos(h) / math.cos(math.pi / 3 - h))
        b = 3 * i - (r + g)
    else:
        h -= 4 * math.pi / 3
        g = i * (1 - s)
        b = i * (1 + s * math.cos(h) / math.cos(math.pi / 3 - h))
        r = 3 * i - (g + b)
    return [int(r), int(g), int(b)]