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javascript放大镜效果的简单实现

2013-12-09 00:00 856 查看

这个效果并不难，要点是位置和比例设置，

捕获鼠标位置、判断鼠标位置区域、还有onmouseover事件、onmousemove事件、onmouseout事件

设置显示大图的比例，小图上显示的切图比例都要弄准确点，最好是2倍啦，4倍啦。

主要注意宽度，我这里的图片m.jpg是1440X900的....

<!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=utf-8">
<title>放大镜效果</title>
<style type="text/css">
*{margin:0;padding:0;}
#smallimg{width:360px;float:left;position:relative;border:1px solid red;}
#smallimg img{ width:360px;}
#bigimg{float:left;width:400px;height:400px;margin-left:40px;border:1px solid #ccc;display:none;}
#showimg{width:100px;height:100px;background:#fff;cursor:move; position:absolute;border:1px solid #666;opacity:0.5;filter:alpha(opacity=50);display:none;}
</style>
</head>
<body>
<div id="smallimg">
 <img src="jq/m.jpg" alt=""/>
 <div id="showimg"> </div>
</div>
<div id="bigimg"> </div>
<script type="text/javascript">
var $=function(id){return typeof id=="string"?document.getElementById(id):id}
var smallimg = $("smallimg");
var showimg = $("showimg");//滤镜图片
var bigimg = $("bigimg");
var small_url = smallimg.getElementsByTagName("img")[0].getAttribute("src");
var show_half = maxWidth = maxHeight = 0;
smallimg.onmouseover = function(){
 showimg.style.display = "block";
 bigimg.style.display = "inline";
 show_half = showimg.offsetHeight/2;
 maxWidth = smallimg.clientWidth - showimg.offsetWidth;
 maxHeight = smallimg.clientHeight - showimg.offsetHeight;
 //上面两个变量指明showimg允许活动的区域
};
smallimg.onmousemove = function(e){
 var e=window.event?window.event:e;
 var num=bigimg.clientWidth/showimg.clientWidth;
 var Top = e.clientY - smallimg.offsetTop - show_half;
 var Left = e.clientX - smallimg.offsetLeft - show_half;
 //获取当前移动的showimg位置 计算方法是 鼠标坐标 - 最外面容器的坐标 - 盒子的宽(高)的/2 
 Top = Top<0?0:Top>maxHeight?maxHeight:Top;
 Left = Left<0?0:Left>maxWidth?maxWidth:Left;
 showimg.style.top = Top + "px";
 showimg.style.left = Left + "px";
 bigimg.style.background = "url("+small_url+") -"+Left*num+"px -"+Top*num+"px no-repeat";
};
smallimg.onmouseout = function(){
 showimg.style.display="none";
 bigimg.style.background ="";
 bigimg.style.display="none"
};
</script>
</body>
</html>

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