说明：  用来实现图片文件的批量缩放（帮班级上传图片，但是图片太大了，太占空间，若一个一个缩小有太费事，于是就有了这个小程序
(Used to achieve the bulk of the picture file scaling (help classes upload images, but the image is too big, takes up too much space, too much trouble if one narrow, so there is this little program)