waitKey (x)的两个作用

waitKey (x)有两个作用：

·It waits for x milliseconds for a key press. If a key was pressed during that time, it returns the key’s ASCII code. Otherwise, it returns -1.

等待x ms，如果在此期间有按键按下，则立即结束并返回按下按键的ASCII码，否则返回-1

·It handles any windowing events, such as creating windows with cv::namedWindow(), or showing images with cv::imshow().
如果x=0，那么无限等待下去，直到有按键按下