本例将实现图像的遮照效果，运行结果：一个椭圆在窗口中移动，椭圆中显示背景图像,椭圆以外为黑色，背景图像被遮住。当鼠标在窗格中移动时，显示背景图像的椭圆跟着鼠标移动-This case image masks the effect of operating results: an oval window mobile, oval display a background image, other than for the black oval, the background image to be covered. Move the mouse in the pane to display the background image of the ellipse with the mouse to move