鼠标画图程序，怎样实现用鼠标在窗口中绘图

单击按钮切换画图状态，然后点击多动鼠标，画橡皮筋矩形，可以画多个。单击任意一个可以缩放。-Click the button to switch drawing, and then click to move the mouse, draw a rubber band rectangle, you can draw multiple. Click on any one can be scaled.