from PIL import Image
import numpy as np
import random

h, w = 512, 512
data = np.zeros((h, w, 3), dtype=np.uint8)

#Draw here
# data[y, x] = [r, g, b]
for y in range(100):
    for x in range(100):
        r = random.randint(0,255)
        g = random.randint(0,255)
        b = random.randint(0,255)
        data[100+y, 100+x] = [r, g, b]

cv2.imwrite('my.png', data)

#or

img = Image.fromarray(data, 'RGB')
img.save('my.png')
img.show()