织梦CMS图片太大自动按比例缩放

<script type="text/javascript">
function resizeImage(ImgD, iwidth, iheight) {
    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;
            }
        }
        ImgD.alt = image.width + "×" + image.height;
    }
}
</script>

<img src="path/to/image.jpg" onload="resizeImage(this, 300, 200)" />