import numpy as np
import cv2

b=np.ones([400,400],dtype='uint8')*255
n=int(50)
for i in range(n,400,n*2):
   for j in range(n,400,n*2):
          b[j-n:j,i-n:i]=0
          b[j:j+n,i:i+n]=0

cv2.imshow('CheckerBoard 8*8',b)
cv2.waitKey(0)
cv2.destroyAllWindows()          
