JS按比例缩放图片

1、JS代码

   <script type="text/javascript" language="javascript">
         var flag = false;
         function DrawImage3(iwidth,iheight,ImgD) {
             var image = new Image();
             image.src = ImgD.src;
             if (image.width >  && image.height > ) {
                 flag = true;
                      //原图宽除高的值和定义宽除高的值的比较
                 if (image.width / image.height >= iwidth / iheight) {
                     // 原图的宽大于定义的宽
                     if (image.width > iwidth) {
                         ImgD.width = iwidth;
                         //定义的宽度和原图的宽度的比例，同比缩小高度
                         ImgD.height = (image.height * iwidth) / image.width;
                     } else {
                         ImgD.width = image.width;
                         ImgD.height = image.height;
                     }
                     ImgD.alt = image.width + "×" + image.height;
                 }
                 else {
                     // 原图的高大于定义的高
                     if (image.height > iheight) {
                         ImgD.height = iheight;
                         //定义的高度和原图的高度的比例，同比缩小宽度
                         ImgD.width = (image.width * iheight) / image.height;
                     } else {
                         ImgD.width = image.width;
                         ImgD.height = image.height;
                     }
                     ImgD.alt = image.width + "×" + image.height;
                 }
             }
         }
     </script>

2、前代代码

 <img alt='' src="Image/wuqilong.jpg" onload="DrawImage3(200,150,this)" />