在对话框中显示图片并具有滚动条的实例，当图片为大尺寸时，可拖动滚动条显示完整图片，这个例子比较常用，但很少有介绍-dialog box shown in the picture and with the rolling of the examples, when images of large size, Movable roll show complete picture, this example is relatively common, but few have introduced