关于为什么要用 if cv2.waitKey(1) & 0xFF == ord('q'): break的解释

On some systems, waitKey() may return a value that encodes more than just the ASCII keycode. (A bug is known to occur on Linux when OpenCV uses GTK as its backend GUI
library.) On all systems, we can ensure that we extract just the SCII keycode by reading the last byte from the return value like this:
keycode = cv2.waitKey(1)
if keycode != -1:
keycode &= 0xFF

或者

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break