此代码用于实现一个图片浏览器，通过文件菜单中的打开菜单可以打开你需要打开的图片，而且还可以在查看菜单里进行背景缩放功能-this code used to achieve a picture browser, through the File menu to open the menu you can open the need to open the pictures, but can also View menu in the background scaling function