import numpy as np

img = np.array([
    [255, 255, 0,   0  ],
    [255, 255, 0,   0  ],
    [0,   0,   255, 255],
    [0,   0,   255, 255]
], dtype=np.uint8)

white_count = np.sum(img == 255)
black_count = np.sum(img == 0)