python_opencv用线段画封闭矩形的实例

如下所示：

def draw_circle(event,x,y,flags,param):
 global ix,iy,drawing,mode,start_x,start_y

if event == cv2.EVENT_LBUTTONDOWN:
   if drawing == False:
     start_x, start_y = x,y
     ix,iy = x,y
     drawing = True
   elif drawing == True:
     cv2.line(img,(ix,iy),(x,y),(0,255,0),3)
     ix, iy = x, y
   print(drawing)
 elif event == cv2.EVENT_MBUTTONDOWN:
   drawing = False

cv2.line(img, (ix, iy), (start_x, start_y), (0, 255, 0), 3)
   print(drawing)

#
 # elif event == cv2.EVENT_RBUTTONUP:
 #   cv2.line(img,(ix,iy),(x,y),(0,255,0),3)
# Next we have to bind this mouse callback function to OpenCV # # window. In the main loop, we should set a keyboard binding for
# key ‘m' to toggle between rectangle and circle.
img = np.zeros((512,512,3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_circle)

while(1):
 cv2.imshow('image',img)
 k = cv2.waitKey(1) & 0xFF
 if k == ord('m'): # 切换模式
   mode = not mode
 elif k == 27:
   break

cv2.destroyAllWindows()

来源：https://blog.csdn.net/qq_25254777/article/details/80238444