对JPanel窗口添加背景图片的程序，可选择将图片居中或拉伸

在JPanel面板上设置背景图片，可选择将图片居中、平铺和拉伸-Set the background image on a JPanel panel, you can the picture centered, tiled, stretched

鼠标跟随效果，鼠标移动时动画跟随移动，像跳跳圈上下拉伸效果(The mouse follows the effect, when the mouse moves, the animation follows the movement, like jumps the circle to pull up and down the drawing effect)