JavaScript实现仿QQ空间图片弹出层效果

<script type="text/javascript">
function imageShow(which_click) {
  var image_path = which_click;
  //alert(image_path);
  var tag_top = Math.max(document.documentElement.scrollTop, document.body.scrollTop);
  //创建底层灰色DIV
  var index_tag = document.createElement("div");
  index_tag.style.cssText = "width:100%;height:"+Math.max(document.body.clientHeight,document.body.offsetHeight,document.documentElement.clientHeight)+"px;position:relative;background:black;top:0;filter: Alpha(Opacity=80);Opacity:0.8;";
  document.body.appendChild(index_tag);
  //index_tag.ondblclick = closeIndexTag;
  index_tag.onclick = closeIndexTag;
  //创建图片DIV
  var img_tag = document.createElement("div");
  img_tag.style.cssText = "font:12px/18px verdana;overflow:auto;text-align:center;position:absolute;width:200px;border:5px solid white;background:white;color:white;left:"+(parseInt(document.body.offsetWidth)/2-100)+"px;top:"+(document.documentElement.clientHeight/3+tag_top)+"px;";
  img_tag.innerHTML = "<div style='padding:10px;background:#cccccc;border:1px solid white'><img src='images/loading.gif' /><br /><br /><b style='color:#999999;font-weight:normal'>Image loading...</b><br /></div>";
  img_tag.oncontextmenu = function() {
    var clsOK=confirm("是否确定关闭图片显示");
    if(clsOK)
      closeIndexTag();
    return false;
  }
  img_tag.onclick = closeIndexTag;
  //img_tag.onmousemove = barDidplay;
  document.body.appendChild(img_tag);
  //构建图片关闭按钮
  var close_tag = document.createElement("div");
  close_tag.style.cssText = "display:none;position:absolute;left:10px;top:10px;color:black;";
  close_tag.innerHTML = "<b style='background:none;border:0px solid white;filter:Alpha(Opacity=50);Opacity:0.5;cursor:pointer;'> 关闭 </b>";
  close_tag.onclick = closeIndexTag;
  var img = new Image();
  img.src = image_path;
  img.style.cssText = "border:1px solid #cccccc;filter: Alpha(Opacity=0);Opacity:0;cursor:pointer";
  img.onload = imgOK();
  function imgOK() {
    var temp = 0;
    var stop_x = false;
    var stop_y = false;
    var img_tag_x = img_tag.offsetWidth;
    var img_tag_y = img_tag.offsetHeight;
    var img_x = img.width;
    var img_y = img.height;
    var scroll_x=document.documentElement.clientWidth;
    var scroll_y=window.innerHeight||document.documentElement.clientHeight;
    var yy = 0;
    var xx = 0;
    if(img_y > scroll_y || img_x > scroll_x){
      yy = scroll_y - 100;
      xx = (img_x / img_y) * yy;
    }else{
      xx = img_x + 4;
      yy = img_y + 3;
    }
    img.style.width=xx-4+'px';
    img.style.height=yy-3+'px';
    var maxTime = setInterval(function() {
      temp += 30;
      if((img_tag_x + temp) < xx) {
        img_tag.style.width = (img_tag_x + temp) + "px";
        img_tag.style.left = (scroll_x - img_tag_x - temp)/2 + "px";
      } else {
        stop_x = true;
        img_tag.style.width = xx + "px";
        img_tag.style.left = (scroll_x - xx)/2 + "px";
      }
      if((img_tag_y + temp) < yy) {
        img_tag.style.height = (img_tag_y + temp) + "px";
        img_tag.style.top = (tag_top + (scroll_y - img_tag_y - temp)/2) + "px";
      } else {
        stop_y = true;
        img_tag.style.height = yy + "px";
        img_tag.style.top = (tag_top + (scroll_y - yy)/2) + "px";
      }
      if(stop_x && stop_y) {
        clearInterval(maxTime);
        img_tag.appendChild(img);
        temp = 0;
        imgOpacity(temp);
      }
    }, 1);
    img_tag.innerHTML="";
    img_tag.appendChild(close_tag);
  }
  function closeIndexTag() {
    document.body.removeChild(index_tag);
    document.body.removeChild(img_tag);
  }
  function imgOpacity(temp_imgOpacity) {
    var temp = temp_imgOpacity;
    temp += 10;
    img.style.filter = "alpha(opacity=" + temp + ")";
    img.style.opacity = temp/100;
    var imgTime = setTimeout(function() {imgOpacity(temp);}, 10);
    if(temp > 100)
      clearTimeout(imgTime);
  }
  var bar_show;
  function barDidplay(){
    clearTimeout(bar_show);
    close_tag.style.display = "block";
    bar_show = setTimeout(function() {close_tag.style.display = "none"}, 1000);
  }
}
</script>

<a class="add" href="javascript:;" onclick="imageShow('img/hn_bg.jpg')">
<span>图片效果</span>
</a>