function ImgShow(evt) {
    var imgTag = (window.event) ? event.srcElement : evt.target;
    var imgPath = imgTag.src.replace("a.jpg", ".jpg"); //取得弹出的大图url
    var tagTop = Math.max(document.documentElement.scrollTop, document.body.scrollTop);
    var tag = document.createElement("div");
    var bWidth = parseInt(document.documentElement.scrollWidth);
    var bHeight = parseInt(document.documentElement.scrollHeight);
    //alert(bHeight);
    //xwxc.style.name="showPic";
    tag.style.cssText = "width:100%; height:" + bHeight + "px; position:absolute; background:black; top:0; filter:Alpha(Opacity=80);Opacity:0.8;";
    tag.ondblclick = function() { var clsOK = confirm("确定要取消图片显示吗?"); if (clsOK) { closes(); } };
    var tagImg = document.createElement("div");
    tagImg.style.cssText = "font:12px /18px verdana;overflow:auto;text-align:center;position:absolute;width:200px;border:5px solid gray;background:gray;color:white;left:" + (parseInt(document.body.offsetWidth) / 2 - 100) + "px;top:" + (document.documentElement.clientHeight / 3 + tagTop) + "px;"
    tagImg.innerHTML = "<div style='padding:10px;background:#cccccc;border:1px solid white'><img src='' /><br /><br /><b style='color:#999999;font-weight:normal'>Image loading...</b><br /></div>";
    var closeTag = document.createElement("div");
    closeTag.style.cssText = "display:none;position:absolute;left:10px;top:10px;background:red;border:1px solid white;yellow:white;filter:Alpha(Opacity=50);Opacity:0.5;cursor:pointer;";
    closeTag.innerHTML = "<b> 关闭 </b>";
    closeTag.onclick = closes;
    document.body.appendChild(tag);
    document.body.appendChild(tagImg);
    var img = new Image();
    img.src = imgPath;
    img.style.cssText = "border:1px solid #cccccc;filter: Alpha(Opacity=0);Opacity:0;";
    tagImg.oncontextmenu = function() { var clsOK = confirm("确定要取消图片显示吗?"); if (clsOK) { closes(); }; return false };
    var barShow, imgTime;
    img.complete ? ImgOK() : img.onload = ImgOK;
    function ImgOK() {
        var Stop1 = false, Stop2 = false, temp = 0;
        var tx = tagImg.offsetWidth, ty = tagImg.offsetHeight;
        var ix = img.width, iy = img.height;
        var sx = document.documentElement.clientWidth, sy = Math.min(document.documentElement.clientHeight, document.body.clientHeight/*opera*/);
        var xx = ix > sx ? sx - 50 : ix + 4, yy = iy > sy ? sy - 50 : iy + 3;
        var maxTime = setInterval(function() {
            temp += 35;
            if ((tx + temp) < xx) {
                tagImg.style.width = (tx + temp) + "px";
                tagImg.style.left = (sx - (tx + temp)) / 2 + "px";
            } else {
                Stop1 = true;
                tagImg.style.width = xx + "px";
                tagImg.style.left = (sx - xx) / 2 + "px";
            }
            if ((ty + temp) < yy) {
                tagImg.style.height = (ty + temp) + "px";
                tagImg.style.top = (tagTop + ((sy - (ty + temp)) / 2)) + "px";
            } else {
                Stop2 = true;
                tagImg.style.height = yy + "px";
                tagImg.style.top = (tagTop + ((sy - yy) / 2)) + "px";
            }
            if (Stop1 && Stop2) {
                clearInterval(maxTime);
                tagImg.appendChild(img);
                temp = 0;
                imgOPacity();
            }
        }, 1);
        function imgOPacity() {
            temp += 10;
            img.style.filter = "alpha(opacity=" + temp + ")";
            img.style.opacity = temp / 100;
            imgTime = setTimeout(imgOPacity, 1)
            if (temp > 100) clearTimeout(imgTime);
        }
        tagImg.innerHTML = "";
        tagImg.appendChild(closeTag);
        if (ix > xx || iy > yy) {
            img.alt = "按住左键拖动,双击放大/缩小";
            img.ondblclick = function() {
                if (tagImg.offsetWidth < img.offsetWidth || tagImg.offsetHeight < img.offsetHeight) {
                    img.style.width = "auto";
                    img.style.height = "00%";
                    img.alt = "双击100%放大";
                    img.onmousedown = null;
                    closeTag.style.top = "10px";
                    closeTag.style.left = "10px";
                    tagImg.style.overflow = "visible";
                    tagImg.style.width = img.offsetWidth + "px";
                    tagImg.style.left = ((sx - img.offsetWidth) / 2) + "px";
                } else {
                    img.style.width = ix + "px";
                    img.style.height = iy + "px";
                    img.alt = "双击可以缩小";
                    img.onmousedown = dragDown;
                    tagImg.style.overflow = "auto";
                    tagImg.style.width = xx + "px";
                    tagImg.style.left = ((sx - xx) / 2) + "px";
                }
            }
            img.onmousedown = dragDown;
            tagImg.onmousemove = barHidden;
            tagImg.onmouseout = moveStop;
            document.onmouseup = moveStop;
        } else {

            tagImg.style.overflow = "visible";
            tagImg.onmousemove = barHidden;
        }
    }
    function dragDown(a) {
        img.style.cursor = "pointer";
        var evts = a || window.event;
        var onx = evts.clientX, ony = evts.clientY;
        var sox = tagImg.scrollLeft, soy = tagImg.scrollTop;
        var sow = img.width + 2 - tagImg.clientWidth, soh = img.height + 2 - tagImg.clientHeight;
        var xxleft, yytop;
        document.onmousemove = function(e) {
            var evt = e || window.event;
            xxleft = sox - (evt.clientX - onx) < 0 ? "0" : sox - (evt.clientX - onx) > sow ? sow : sox - (evt.clientX - onx);
            yytop = soy - (evt.clientY - ony) < 0 ? "0" : soy - (evt.clientY - ony) > soh ? soh : soy - (evt.clientY - ony);
            tagImg.scrollTop = yytop;
            tagImg.scrollLeft = xxleft;
            closeTag.style.top = (yytop + 10) + "px";
            closeTag.style.left = (xxleft + 10) + "px";
            return false;
        }
        return false;
    }
    function barHidden() {
        clearTimeout(barShow);
        if (closeTag.style.display == "none") closeTag.style.display = "block";
        barShow = setTimeout(function() { closeTag.style.display = "none"; }, 2000);
    }
    function closes() {
        document.body.removeChild(tag);
        document.body.removeChild(tagImg);
        clearTimeout(barShow);
        clearTimeout(imgTime);
        document.onmouseup = null;
        tag = img = tagImg = closeTag = null;
    }
    function moveStop() {
        document.onmousemove = null;
        tagImg.onmousemove = barHidden;
        img.style.cursor = "default";
    }
}