先安装opencv-contrib-python

pip install opencv-contrib-python

 再换源安装opencv-python

pip install opencv-python  -i https://pypi.tuna.tsinghua.edu.cn/simple 

如果出现

使用这个，3.6环境下不能安装opencv的最新版本 

pip install opencv-python==4.5.5.62 -i https://pypi.tuna.tsinghua.edu.cn/simple