js实现图片等比缩放

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//图片等比例缩放
 
 
 
 
<html>
 
<head>
 
<title>等比例缩放图片</title>
 
<script>
 
function DrawImage(ImgD,iwidth,iheight){   
 
    //参数(图片,允许的宽度,允许的高度)   
 
    var image=new Image();   
 
    image.src=ImgD.src;   
 
    if(image.width>0 && image.height>0){   
 
      if(image.width/image.height>= iwidth/iheight){   
 
          if(image.width>iwidth){     
 
              ImgD.width=iwidth;   
 
              ImgD.height=(image.height*iwidth)/image.width;   
 
          }else{   
 
              ImgD.width=image.width;     
 
              ImgD.height=image.height;   
 
          }   
 
      }else{   
 
          if(image.height>iheight){     
 
              ImgD.height=iheight;   
 
              ImgD.width=(image.width*iheight)/image.height;           
 
          }else{   
 
              ImgD.width=image.width;     
 
              ImgD.height=image.height;   
 
          }   
 
      }   
 
    }   
 
}  
 
</script>
 
</head>
 
<body>
 
<img src="/images/logo.gif" alt="自动缩放后的效果" width="220" height="80" onload="javascript:DrawImage(this,100,100)" />
 
</body>
 
</html>