После преобразования RGB матрицы в CMY матрицу получаю чёрное изображение

from PIL import Image
import numpy as np
 
img_rgb = Image.open('s.png')
rgb_matr = np.asarray(img_rgb.convert('RGB'))
rgb_rows, rgb_cols, rgb_d = rgb_matr.shape
cmyk_matr = np.zeros(shape = (rgb_rows, rgb_cols, 4), dtype = 'uint8')
 
RGB_coeff = 255
CMYK_coeff = 100
 
def rgb_to_cmyk(*args):
 
    r = args[0]
    g = args[1]
    b = args[2]
 
    if(r, g, b) == (0, 0, 0):
        return 0, 0, 0, CMYK_coeff
 
    c = 1 - r / RGB_coeff
    m = 1 - g / RGB_coeff
    y = 1 - b / RGB_coeff
 
    min_cmy = min(c, m, y)
    c = (c - min_cmy)/(1 - min_cmy)
    m = (m - min_cmy)/(1 - min_cmy)
    y = (y - min_cmy)/(1 - min_cmy)
    k = min_cmy
 
    return int(c * CMYK_coeff), int(m * CMYK_coeff), int(y * CMYK_coeff), int(k * CMYK_coeff)
 
for item1 in rgb_matr:
    i = 0
    for item2 in item1:
        j = 0
        cmyk_matr[i][j] = np.asarray(rgb_to_cmyk(*item2))
        j += 1
    i += 1
 
img_cmy = Image.fromarray(cmyk_matr, 'RGBA')
img_cmy.save('CMY.png')

i = 0
for item1 in rgb_matr:
    j = 0
    for item2 in item1:
        cmyk_matr[i][j] = np.asarray(rgb_to_cmyk(*item2))
        print(cmyk_matr[i][j])
        j += 1
    i += 1