function getImgInfo(url){

         var img = new Image(), loaded = false;

         var info = {};

         //对于预加载的情况,即没有把图片插入DOM树

         img.onload = function(){

             img.onload = null;

             loaded = true;  //标志当前已加载过，防止complete再运行

             info['width'] = img.width;

             info['height'] = img.height;

         }

         img.src = url;

         var orignInfo;

         //已经加载过的图片

         if(img.complete && !loaded){

             //safari,firefox,chrome,与opera10+中，有两个便捷的属性

             if(img.naturalWidth && img.naturalHeight){

                 info['width'] = img.naturalWidth;

                 info['height'] = img.naturalHeight;

             }else if(img.runtimeStyle){

                 //IE runtimeStyle不用同步style就能重绘原来的元素

                 orignInfo = {'width':img.width,'height':img.height};   //保存原来的尺寸

                 img.width = img.height = "auto";//重写

                 info['width'] = img.width;//获取原始尺寸

                 info['height'] = img.height;

                 img.width = orignInfo.width;  //还原尺寸

                 img.height = orignInfo.height;

             }else{

                 info['width'] = img.width;

                 info['height'] = img.height;

             }

         }

         return info;

     }