if cv2.waitKey(1) & 0xff == ord('q'):break的理解

v2.waitKey(1)
1为参数，单位毫秒ms，表示读帧间隔时间
ord(’ ')

将字符转化为对应的整数（ASCII码）

关于0xFF

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) o
if keycode != -1: 
keycode &= 0xFF

感谢这些大哥的博客帮助：
https://www.jianshu.com/p/30c40d7ce5dc
https://www.jianshu.com/p/b0d3221b0d81
https://blog.csdn.net/zhaowei5210/article/details/70920711