import cv2

import numpy as np

filename = 'small.png'

img = cv2.imread(filename)

img2 = np.float32(img)

dst = cv2.cornerHarris(img2,2,3,0.04)

#result is dilated for marking the corners, not important

dst = cv2.dilate(dst,None)

# Threshold for an optimal value, it may vary depending on the image.

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

cv2.imshow('dst',img)

if cv2.waitKey(0) & 0xff == 27:

cv2.destroyAllWindows()