使用mfc加载图片，随图片放大出现滚动条。(load image,it has scrollbar when the image is larged)

对网上的代码进行了修改，实现了V. Scroll Control和H. Scroll Control，以贴图实现拖拉控件(The code on the network has been modified, to achieve the V. Scroll Control and H. Scroll Control, to achieve drag control map)