function resizeimg(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;
            }
            ImgD.alt = image.width + "×" + 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;
        }
        ImgD.style.cursor = "pointer"; //改变鼠标指针 
        ImgD.onclick = function() { window.open(this.src); } //点击打开大图片 
        if (navigator.userAgent.toLowerCase().indexOf("ie") > -1) { //判断浏览器，如果是IE 
            ImgD.title = "请使用鼠标滚轮缩放图片，点击图片可在新窗口打开";
            ImgD.onmousewheel = function img_zoom() //滚轮缩放 
            {
                var zoom = parseInt(this.style.zoom, 10) || 100;
                zoom += event.wheelDelta / 12;
                if (zoom > 0) this.style.zoom = zoom + "%";
                return false;
            }
        } else { //如果不是IE 
            ImgD.title = "点击图片可在新窗口打开";
        }
    }
}