js等比例缩放图片

  $.fn.DrawImage = function(options) { 
          return this.each(function(index) { 
            var $this = jQuery(this); 
       
            var opts = jQuery.extend({ 
                     width:150, 
                     height:150 
                 }, options || {} 
            ); 

           var flag=false; 
          
          if($this.width()>0 && $this.height()>0){ 
             flag=true; 
 
             if($this.width()/$this.height()>= opts.width/opts.height){ 
                 if($this.width()>opts.width){ 
                     $this.width(opts.width); 
                     $this.height(($this.height()*opts.width)/$this.width()); 
                 } 
             }else{ 
                 if($this.height()>opts.height){ 
                     $this.height(opts.height); 
                     $this.width(($this.width()*opts.height)/$this.height()); 
                 } 
                  
             } 
 
             $this.css("display","inline"); 
         } 
      }); 
  }; 

保存以上代码为 DrawImage.js需另外引用jquery.js

用法：
$(document).ready(function(){
  $("img").DrawImage({width: 270, height: 270}); 
});