I have an encryption algorithm, but I am unsure how to reverse the modulus that was performed. How do i do this? [closed]

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Closed 23 hours ago.

I have this encryption code, but I am unsure how to invert the modulus used in the code:

from PIL import Image

flag = Image.open(r"flag.png")
img = array(flag)

key = [41, 37, 23]

a, b, c = img.shape

for x in range (0, a):
    for y in range (0, b):
        pixel = img[x, y]
        for i in range(0,3):
            pixel[i] = pixel[i] * key[i] % 251
        img[x][y] = pixel

enc = Image.fromarray(img)
enc.save('enc.png')

来源：https://stackoverflow.com/questions/60696879/i-have-an-encryption-algorithm-but-i-am-unsure-how-to-reverse-the-modulus-that