代码简介：
CSS+Js图片切换技术，类似的已有不少了，这一个使用了遮罩过渡的效果，同样应用到了TAB选项卡上，本页面仅是为了演示，大家用时候把它拆分开来，这个效果也对学习图片效果制作很有帮助。
代码内容：
View Code
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>CSS+JS控制遮罩效果的TAB及焦点图片切换（荐） - www.webdm.cn</title>
<style>
div, ul, ol, li, dl, dt, dd {
margin:0;
padding:0;
}
.imgFlash,.tab{margin:auto}
/*------焦点图片的css-------*/
.imgFlash {
height:230px;270px;
position:relative;
}
.imgFlash dl {
height:100%;
overflow:hidden;
position:absolute;
100%;
}
.imgFlash img {
height:100%;
position:absolute;
100%;
background-color: #FFFFFF;
background-repeat: no-repeat;
background-position: center center;
}
.imgFlash dt {
bottom:0;
font-size:12px;
height:24px;line-height:24px;
left:0;
position:absolute;
100%;
z-index:1;
}
.imgFlash dt span {
background-color:#000000;
height:100%;
opacity:0.4;filter:Alpha(Opacity=40);
position:absolute;
100%;
}
.imgFlash dt a {
color:#FFFFFF;
position:absolute;
text-decoration:none;
text-indent:5px;
z-index:1;
}
.imgFlash dt a:hover {
text-decoration:underline;
}
.imgFlash div {
bottom:8px;
cursor:pointer;
display:block;
position:absolute;
right:8px;
z-index:99999;
}
.imgFlash div em {
background-color:#000000;
border:1px solid #FFFFFF;
display:block;
float:right;
height:4px;
margin-right:3px;
filter:Alpha(Opacity=50);opacity:0.5;
overflow:hidden;
4px;
}
.imgFlash div em.d {/*激活的小方块的样式*/
background-color:#CC0000;
filter:Alpha(Opacity=80);
opacity:0.8;
}
/*-------------------------Tab的css----------------------------*/
.tab,.tab ul{list-style-type: none;}
.tab{
270px;
background-color:#FFFFFF;
height: 160px;
font-size: 12px;
position: relative;
border-top- 30px;
border-right- 1px;
border-bottom- 1px;
border-left- 1px;
border-top-style: solid;
border-right-style: solid;
border-bottom-style: solid;
border-left-style: solid;
border-top-color: #0066FF;
border-right-color: #0066FF;
border-bottom-color: #0066FF;
border-left-color: #0066FF;
}
.tab ul {
position: absolute;
top: -30px;
}
.tab li{
float:left;
background-color:#A9CEEB;
background-repeat:no-repeat;
background-position:left top;
margin-top:5px;
margin-left: 5px;
}
.tab li.d {
background-color: #FFFFFF;
}
.tab li a{text-decoration:none;display:block;padding-right:8px;padding-left:8px;line-
height:25px;color:#2B6FA2;}
.tab li.d a{color:#0C3E74;}
.tab li ul{
border-bottom-style:none;
position:absolute;
left:0px;
top:30px;
background-color: #FFFFFF;
padding-top: 10px;
270px;
}
.tab li li{
float:none;
background-image:none;
margin:0px;
background-color: #FFFFFF;
}
.tab li li a{
background-image:none;
line-height:22px;
color: #000000;
float: none;
height: 22px;
}
.tab li ul li a:hover{text-decoration:underline;}
.tab li.d li a{color:#000000;}
</style>
<script language="javascript">
var $ = function (d){return document.getElementById( d );};
var isIE = (document.all) ? true : false;
var Bind = function (obj,fun,arr){return function() {arr || (arr = arguments);return fun.apply
(obj,arr);}};//绑定
var Tween = function(t,b,c,d){return c*t/d + b;};//缓冲函数
function addEventHandler(oTarget, sEventType, fnHandler) {if (oTarget.addEventListener)
{oTarget.addEventListener(sEventType, fnHandler, false);} else if (oTarget.attachEvent)
{oTarget.attachEvent("on" + sEventType, fnHandler);} else {oTarget["on" + sEventType] = fnHandler;
}
};//事件监听
function removeEventHandler(oTarget, sEventType, fnHandler) {
if (oTarget.removeEventListener) {
oTarget.removeEventListener(sEventType, fnHandler, false);
} else if (oTarget.detachEvent) {
oTarget.detachEvent("on" + sEventType, fnHandler);
} else {
oTarget["on" + sEventType] = null;
}
};//移除监听
var Timer = {};//Timer
Timer.add = function (fn){return new this.fn(fn)};
Timer.fn = function (fn){
var timer;
this.play = function (speed,only){
speed || ( speed = 10 );
if(only)timer = window.setTimeout(fn,speed);
else timer = window.setInterval(fn,speed);
};
this.stop = function (){clearTimeout(timer);clearInterval(timer)};
};
//Mask 遮罩动画
var Mask = function (){
this.fl = Timer.add(Bind(this,this.fn));
this.from_num = 0;
this.speed = 50;//动画速度，越大越慢
};
Mask.prototype.ready = function (ele,pos){
if(this.ele)this.set(this.maxWidth,this.maxHeight);
this.ele = ele;
this.maxWidth = this.ele.offsetWidth;
this.maxHeight = this.ele.offsetHeight;
this.ele.style.position = "absolute";
this.from_num = 0;
if(!pos){
var x = ["left","center","right",""][parseInt(4*Math.random())],
y = ["top","center","bottom",""][parseInt(4*Math.random())];
if(x == "" && y == "")x = "left";//避免同时为""
this.position = [x,y];
}else{
this.position = pos;
}
this.set(0,0);
this.fl.stop();
};
Mask.prototype.start = function (){this.fl.play();};
Mask.prototype.stop = function (){this.fl.stop();};
Mask.prototype.set = function (width,height){//设置遮罩的矩形，用于定位遮罩的变换方向
var t,r,b,l;
switch(this.position[0]){
case "left" :
l = 0;
r = width;
break;
case "center" :
l = (this.maxWidth - width)/2;
r = (this.maxWidth + width)/2;
break;
case "right" :
l = this.maxWidth - width;
r = this.maxWidth;
break;
default:
l = 0;
r = this.maxWidth;
}
switch(this.position[1]){
case "top" :
t = 0;
b = height;
break;
case "center" :
t = (this.maxHeight - height)/2;
b = (this.maxHeight + height)/2;
break;
case "bottom" :
t = this.maxHeight - height;
b = this.maxHeight;
break;
default :
t = 0;
b = this.maxHeight;
break;
}
this.ele.style.clip = "rect("
+ t + "px,"
+ r + "px,"
+ b + "px,"
+ l + "px)" ;
};
Mask.prototype.fn = function (){
var w,h;
this.from_num ++ ;
if(this.from_num<=this.speed){
w = Tween(this.from_num,0,this.maxWidth,this.speed);
h = Tween(this.from_num,0,this.maxHeight,this.speed);
this.set(w,h);
}else{
this.fl.stop();
//this.start();//若不需要重复动画，把这句注释，上句不注释
}
};
function ImgFlash(box){
this.box = box.getElementsByTagName("dl");
this.ge = 4;//切换间隔秒数
this.menu = [];
this.mask = new Mask();//加载遮罩动画，不设置参数 即 随机效果
this.zIndex = this.box.length;
var _div = document.createElement('div');
this.dang = 0;
for(i=0;i<this.zIndex;i++){
this.box[i].style.zIndex = this.zIndex-i;
var _em = document.createElement('em'),_span = document.createElement
('span');
var _dt = this.box[i].getElementsByTagName("dt")[0];
_dt.appendChild(_span);
addEventHandler(_em,'mouseover',Bind(this,this.emEvent,[this.zIndex-i-
1,true]));
_div.appendChild(_em);
this.menu.push(_em);
if(this.zIndex-i==1){
_em.className = 'd';
}
}
box.appendChild(_div);
addEventHandler(box,'mouseover',Bind(this,function(){this.fl.stop()}));
addEventHandler(box,'mouseout',Bind(this,function(){this.fl.play(this.ge*1000)}));
this.fl = Timer.add(Bind(this,this.enterFrame))
this.fl.play(this.ge*1000);
}
ImgFlash.prototype.enterFrame = function(){
var ddd = this.dang==2?0:this.dang+1;
this.emEvent(ddd);
};
ImgFlash.prototype.emEvent = function (index,b){
if(b)this.fl.stop();
if(index == this.dang)return;
this.menu[this.menu.length-1-this.dang].className="";
var odl = this.box[this.dang];
this.zIndex++;
this.dang = index;
this.menu[this.menu.length-1-this.dang].className="d";
var ndl = this.box[this.dang];
var img = ndl.getElementsByTagName("img")[0];
this.mask.ready(img);
this.mask.start();
ndl.style.zIndex = this.zIndex;
}
function Tab(id,type){
var nav = id.getElementsByTagName("ul")[0].childNodes;
var _nav,i=0;
this.mask = new Mask();//初始化遮罩动画
this.z = 1000;
while(_nav = nav[i++]){
if(_nav.className=="d")this.focusEle = _nav;
if(_nav.childNodes.length>1){
var A = _nav.getElementsByTagName("A")[0];
addEventHandler(A,type,Bind(this,fun,[A]));
}
if(_nav.nodeType == 1)_nav.getElementsByTagName("UL")[0].style.zIndex = nav.length-i;
}
function fun(ele){
var li = ele.parentNode;
var ul = li.getElementsByTagName("UL")[0];
this.z += 1
ul.style.zIndex = this.z;
if(li.className=="d")return;
li.className+=(li.className.length>0? " ": "") + "d";
this.focusEle.className=this.focusEle.className.replace(/( ?|^)d\b/g, "");
this.focusEle = li;
this.mask.ready(ul);
this.mask.start();
};
}
</script>
</head>
<body>
<div class="imgFlash" id="box">
<dl>
<dt><a href="#">神秘花园</a></dt>
<dd><a href="#"><img src="http://www.webdm.cn/images/wall1_s.jpg" border="0" /></a></dd>
</dl>
<dl>
<dt><a href="#">网页代码站</a></dt>
<dd><a href="#"><img src="http://www.webdm.cn/images/wall2_s.jpg" border="0" /></a></dd>
</dl>
<dl>
<dt><a href="#">人间仙境</a></dt>
<dd><a href="#"><img src="http://www.webdm.cn/images/wall3_s.jpg" border="0" /></a></dd>
</dl>
</div>
<br />
<br />
<br />
<br />
<div class="tab" id="tab1">
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</li>
</ul>
</div>
<script>
new ImgFlash($("box"));//初始化
new Tab($("tab1"),"mouseover");
</script>
</body>
</html>
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代码来自：http://www.webdm.cn/webcode/d85075ed-26ff-46ce-9668-fd2f48c3b2a7.html