cv2.waitKey(x)解析

1.函数说明

def waitKey(delay=None): # real signature unknown; restored from __doc__
    """
    waitKey([, delay]) -> retval
    .   @brief Waits for a pressed key.
    .   
    .   The function waitKey waits for a key event infinitely (when \f$\texttt{delay}\leq 0\f$ ) or for delay
    .   milliseconds, when it is positive. Since the OS has a minimum time between switching threads, the
    .   function will not wait exactly delay ms, it will wait at least delay ms, depending on what else is
    .   running on your computer at that time. It returns the code of the pressed key or -1 if no key was
    .   pressed before the specified time had elapsed.
    .   
    .   @note
    .   
    .   This function is the only method in HighGUI that can fetch and handle events, so it needs to be
    .   called periodically for normal event processing unless HighGUI is used within an environment that
    .   takes care of event processing.
    .   
    .   @note
    .   
    .   The function only works if there is at least one HighGUI window created and the window is active.
    .   If there are several HighGUI windows, any of them can be active.
    .   
    .   @param delay Delay in milliseconds. 0 is the special value that means "forever".
    """
    pass

2.解释

函数waitKey无限地等待一个按键产生的事件即者当它为正数时，等待延迟时间单位为毫秒。由于操作系统在切换线程之间的时间最短，该函数将不会等待确切的延迟ms，它将等待至少延迟ms，这取决于当时在您的计算机上运行的其他内容。它返回按下的键的代码，如果在指定的时间之前没有按下键，则返回-1。
简而言之如果有正数x输入则 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
如果x=0，那么无限等待下去，直到有按键按下