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