import numpy as np 
import cv2

filename = 'chess.jpg'
img = cv2.imread(filename)
gray = cv2.cvtColor (img, cv2.COLOR_BGR2GRAY)
gray = np.float32(gray)

dst = cv2.cornerHarris(gray,2, 3, 0.04)
dst = cv2.dilate (dst, None)

img[dst>0.01*dst.max()] = [0,0,255]

cv2.imshow('dst', img)
if cv2.waitKey(0) & 0xFF == 27:
    cv2.destroyAllWindows()