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 > 0 && image.height > 0) {
                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)" />