解决OpenCV使用SURF，SIFT等的问题

由于该算法被申请了专利，将opencv版本退到3.4.2即可解决，卸载之前的包，

pip uninstall opencv-python
pip uninstall opencv-contrib-python

然后

pip install -i https://pypi.tuna.tsinghua.edu.cn/simple opencv-python==3.4.2.16
pip install -i https://pypi.tuna.tsinghua.edu.cn/simple opencv-contrib-python==3.4.2.16

问题即可解决