<!DOCTYPE html>
<html>
<head>
<title>放大镜效果</title>
<meta charset="utf-8">
<style type="text/css">
body{position: relative;}
*{margin: 0;padding:0;}
#Box{
height:300px;
width:300px;
position: relative;
border:1px solid gray;
}
#bigBox{
height:300px;
width:300px;
position: absolute;
top:0;
left:310px;
overflow: hidden;
display:none;
border: 1px solid gray;
}
#Box img{
height:300px;
width:300px;
}
#lay{
background:#fff;
border:1px solid gray;
position: absolute;
top:0;
left: 0;
opacity:0.5;
display:none;
filter:alpha(opacity=50);
}
</style>
<script type="text/javascript">
window.onload = function(){
var Box = document.getElementById("Box");
var bigBox = document.getElementById("bigBox");
var bigbox = bigBox.children[0];
var lay = document.getElementById("lay");
//鼠标移入时，将放大镜和bigBox显示出来
Box.onmouseover = function(){
lay.style.display = "block";
bigBox.style.display = "block";
}
//鼠标移出时，将放大镜和bigBox隐藏起来
Box.onmouseout = function(){
lay.style.display = "none" ;
bigBox.style.display = "none";
}
Box.onmousemove = function(e){
e = e || event;//事件源的兼容问题
var scale = 4;//图片的放缩比例
//将鼠标放到放大镜的中间
var x = e.clientX - lay.offsetWidth/2;
var y = e.clientY - lay.offsetHeight/2;
//将放大镜的宽高与盒子的宽高结合起来按比例放缩
lay.style.width = parseInt(Box.offsetWidth / scale )+ "px";
lay.style.height = parseInt(Box.offsetHeight / scale)+ "px";
//设置大盒子的宽高
bigbox.style.width = Box.offsetWidth * scale + "px";
bigbox.style.height = Box.offsetHeight * scale + "px";
if(x < 0){
x = 0;//左边界的判断，当超出时将x置为0;
}
//右边界的判断，当超出时将x置为Box的宽度减去放大镜的宽度;
if( x >= Box.offsetWidth - lay.offsetWidth){
x = Box.offsetWidth - lay.offsetWidth;
}
//下边界的判断，当超出时将y置为Box的高度减去放大镜的高度;
if( y >= Box.offsetHeight - lay.offsetHeight){
y = Box.offsetHeight - lay.offsetHeight;
}
if(y < 0){
y = 0;//上边界的判断，当超出时将y置为0;
}
lay.style.left = x + "px";
lay.style.top = y + "px";
// 同比例放缩，大的盒子图片的放缩比例，当小盒子向右移动的时候，大盒子向左移动同等的比例的宽高，方向是相反的
var left = lay.offsetLeft * scale;
var top = lay.offsetTop * scale ;
bigbox.style.marginLeft =(left * (-1)) + "px";
bigbox.style.marginTop =(top * (-1))+ "px";
}
}
</script>
</head>
<body>
<div id="Box">
<img src="1.jpg" alt=""/>
<span id="lay"></span>
</div>
<div id="bigBox">
<img src="1.jpg" alt=""/>
</div>
</body>
</html>
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