https://blog.csdn.net/program_developer/article/details/79677557
https://blog.csdn.net/imbenben/article/details/78046997
https://blog.csdn.net/weixin_39912556/article/details/80512173
http://python.jobbole.com/86236/
python2 -m pip install opencv-python -i https://pypi.tuna.tsinghua.edu.cn/simple