import cv2
import numpy as np

img = cv2.imread("xuehua.png")
# cv2.imshow("Wave",img)
# cv2.waitKey(0)
#we readed the image

mask = np.zeros(img.shape[:2],dtype="uint8")
(cx,cy) = (img.shape[1]/2,img.shape[0]/2)
cv2.rectangle(mask,(cx-75,cy-75),(cx+75,cy+75),255,-1)
# cv2.imshow("Mask",mask)
# cv2.waitKey(0)

masked = cv2.bitwise_and(img,img,mask=mask)
cv2.imshow("Masked",masked)
cv2.waitKey(0)