for C++
https://www.learnopencv.com/install-opencv-4-on-raspberry-pi/
OpenCV 4的安裝，主要是用python
https://www.pyimagesearch.com/2018/09/26/install-opencv-4-on-your-raspberry-pi/
但4.0應該是拿掉pkg-config的部分
https://github.com/opencv/opencv/issues/13154
https://github.com/opencv/opencv/issues/13245
https://github.com/opencv/opencv/issues/13154
在網路上找到一篇超詳細的教學，還有許多細節的提醒與延伸技巧，另外順便解了我對SIFT和SUFT的問題。