通过调用opencv库中的一些函数，实现video的播放，同时在video上叠加一些字符串。-through calling the functions of opencv, a video is played and some strings are added on the frames of the video.

调用opencv函数，读入一幅图像，并且在图像上显示文本字符串-Call opencv function reads an image, and in the text string displayed on the image