利用鼠标进行绘图:点击窗口中的空白处，得到一张“笑脸”的图像；点击已存在的图像，图像在“笑脸”和“哭脸”之间切换；用鼠标可以对图像进行拖动操作；在窗口左上角，显示当前鼠标光标的位置-Plotting the use of the mouse: click on an empty area of ​ ​ the window, the image of a "smiley"click on the image, image to switch between "smiley"and"sad" drag operation with the mouse on the image　 in the upper-left corner of the window displays the current mouse cursor position