图片处理，进行等比例缩放，对于上传的图片可按需缩放。-Image processing, for such scaling, the uploaded image can be scaled on demand.

jquery-backstretch 是一个用来实现全屏按比例缩放背景图片的jQuery插件，兼容大部分浏览器，但IE6和IE7的支持不理想。-jquery-backstretch is used to achieve fullscreen scaled background image jQuery plugin, compatible with most browsers, IE6 and IE7 support is not ideal.