在终端输入：pip install cv2
出现错误提示：
ERROR: Could not find a version that satisfies the requirement cv2 (from versions: none )
ERROR: No matching distribution found for cv2
原因：
没有名为cv2的库，将命令改为：pip install opencv-python
安装成功！
如果还是有错误，将命令改为：pip install opencv-contrib-python