1 import numpy as np
 2 import matplotlib.pyplot as plt
 3 from numpy.core.defchararray import count
 4 import cv2 as cv
 5 
 6 
 7 drawing = False  #按下滑鼠為真
 8 ix, iy = -1, -1
 9 
10 def draw_rectangle(event, x, y, flags, param):
11     global ix, iy, drawing, img
12     if event == cv.EVENT_LBUTTONDOWN:
 
13         print("you has choosen the start point of the rectangle")
14         drawing = True
15         ix, iy = x, y
16     elif event == cv.EVENT_MOUSEMOVE:
17         if drawing == True:
18             px, py = x, y
19             img = mask.copy()  #每次繪製使用一個原始的影象的copy， 這樣繪製矩形框時，就沒有問題  這裡是關鍵
20             cv.rectangle(img, (ix, iy), (px,py),(255, 0, 255), -1)  
 
21     elif event == cv.EVENT_LBUTTONUP:
22         drawing = False
23         px, py = x, y
24         cv.rectangle(img, (ix, iy), (px, py),(255, 0, 255), -1)
25     
26 img_source = cv.imread("duo.jpg")
27 img = np.zeros(img_source.shape)
28 mask = img.copy() #拷貝一個原圖，用以更新背景
29 cv.namedWindow('image
 
', cv.WINDOW_AUTOSIZE)
30 cv.setMouseCallback("image", draw_rectangle)
31 while True:
32     if cv.waitKey(1) == 27:  #esc退出視窗
33         break
34     cv.imshow("image", img)    
35     
36 cv.destroyAllWindows()
37