not enough values to unpack (expected 3, got 2)问题解决
返回三个值只支持opencv3.4.3.18以下版本:image,contours,hierarchy=cv2.findContours(r,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)OpenCV4.*版本中返回值只有两个如下修改:contours,hierarchy=cv2.findContours(r,cv2.RETR_EXTERNAL,cv2.CHA