<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<script>
window.onload = function(){
var img = document.getElementById("img");
if(myBrowser() == "FF"){
img.addEventListener("DOMMouseScroll",fun,false);
}else{
img.onmousewheel = fun;
}
};
function fun(e){
var ev = e || window.event;
var mun = ev.wheelDelta || ev.detail;
if(mun>0){
img.style.width = img.offsetWidth*1.2 + "px";
}else{
img.style.width = img.offsetWidth*0.8 + "px";
}
}
function myBrowser() {
var userAgent = navigator.userAgent; //取得浏览器的userAgent字符串
var isOpera = userAgent.indexOf("Opera") > -1;
//判断是否Opera浏览器
if(isOpera) {
return "Opera";
}
//判断是否Firefox浏览器
if(userAgent.indexOf("Firefox") > -1) {
return "FF";
}
if (userAgent.indexOf("Chrome") > -1) {
return "Chrome";
}
if (userAgent.indexOf("Safari") > -1) {
return "Safari";
}
if (userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1 && !isOpera) {
return "IE";
}
}
</script>
</head>
<body>
<img src="./图片放大图片/imgA_2.jpg" id="img"/>
</body>
</html>
原文：http://www.cnblogs.com/lidongrain/p/5004690.html