from PIL import Image


img = Image.open("56.jpg")


pixels = img.load()


for i in range(img.width):
    for j in range(img.height):

        r, g, b = pixels[i, j]
        S = (r + g + b) // 3

        pixels[i, j] = (S, S, S)


img.show()


img.save("14.jpg")