python中的OpenCV函数 waitkey
函数原型：waitKey(int delay=0)函数说明：The function waitKey waits for a key event infinitely (when delay ≤ 0 ) or for delay milliseconds, when it is positive.翻译：当delay≤ 0，将无限期的等待下去；当delay>0时，就是等待delay毫秒。
