Raspberry3安裝Python3+OpenCV

預設應該有安裝Python3，沒有的話執行

#sudo    apt-get   install python3 idle3

安裝OpenCV

#pip3 install opencv-python

安裝舊版OpenCV

#pip3 install opencv-contrib-python

#sudo apt-get install -y libatlas-base-dev libhdf5-dev libhdf5-serial-dev libatlas-base-dev libjasper-dev  libqtgui4  libqt4-test

出現找不到cv2.face錯誤，重新安裝opencv-contrib-python版本，太新的版本沒有cv2.face，降版到3.4.3.18

#pip3 install --force-reinstall opencv-contrib-python==3.4.3.18

Python3.9需要降版到4.5.4.58

#pip install opencv-contrib-python==4.5.4.58