图片(img标签)大小自适应

 $(function(){
              var myimg,oldwidth,oldheight;
                var maxwidth=249;
                var maxheight=187;
                var imgs = document.getElementsByTagName('img'); 

                for(i=0;i<imgs.length;i++){
                  myimg = imgs[i];

                  if(myimg.width > myimg.height)
                  {
                      if(myimg.width > maxwidth)
                      {
                         oldwidth = myimg.width;
                         myimg.height = myimg.height * (maxwidth/oldwidth);
                         myimg.width = maxwidth;
                      }
                  }else{
                      if(myimg.height > maxheight)
                      {
                         oldheight = myimg.height;
                         myimg.width = myimg.width * (maxheight/oldheight);
                         myimg.height = maxheight;
                      }
                  }
                }
         })