局部放大效果、插件

HTML部分

</head>
<script type="text/javascript" src="js/fangda.js"></script>
<body>
<div id="main">
<img src="http://www.jq22.com/img/cs/500×500-1.png">
</div>
</body>
</html>

CSS部分

#main {
margin:30px;
}
#main img {
width:200px;
height:200px;
}

JS部分

window.onload = function() {
fangda('main', 120, 100, 'blue', 0.6, 3, 'http://www.jq22.com/img/cs/500×500-1.png')
}

//window.onload 之后图片才加载完，才能获取宽高
var fangda = function(mainId, boxWidth, boxHeight, bgcolor, opacity, multiple, imgsrc) {
//获取主容器
var main = document.getElementById(mainId);
//获取图片
var img = main.getElementsByTagName('img')[0];
//获取图片宽高，设置给其父容器
var imgW = img.offsetWidth;
var imgH = img.offsetHeight;
main.style.width = imgW + 'px';
main.style.height = imgH + 'px';
main.style.position = 'relative';
//hidden为了后面的方块在鼠标移出后消失
main.style.overflow = 'hidden';
//动态创建放大的小方块，设置属性，并且添加到main内
var box = document.createElement("div");
box.style.width = boxWidth + 'px';
box.style.height = boxHeight + 'px';
box.style.backgroundColor = bgcolor;
box.style.opacity = opacity;
//设置绝对定位时，要想起来给其父容器设置相对定位
box.style.position = 'absolute';
box.style.top = 0;
box.style.left = 0;
box.style.cursor = 'move';
//none是为了一开始隐藏，鼠标移入main再显示
box.style.display = 'none';
main.appendChild(box);

//给main添加鼠标移入事件
//移入显示box
main.onmouseover = function() {
box.style.display = 'block';
showBox.style.display = 'block';
showBox.style.zIndex = 999;
}
//移出隐藏box
main.onmouseout = function() {
box.style.display = 'none';
showBox.style.display = 'none';
showBox.style.zIndex = -999;
}
//设置main的鼠标移动事件，带着box走
//提前获取一些值
//获取main距离左边与顶部的距离
var mainL = main.offsetLeft;
var mainT = main.offsetTop;
//获取main和box的宽高;
var mainW = main.offsetWidth;
var mainH = main.offsetHeight;
//getComputedStyle(box).width获取到的是带有单位px的值，需要转化为整数
var boxW = parseInt(getComputedStyle(box).width);
var boxH = parseInt(getComputedStyle(box).height);

//动态创建显示的容器以及其内的图片,为了使用mainL等已经获取的值
//并且设置其属性
var showBox = document.createElement("div");
showBox.style.width = boxWidth * multiple + 'px';
showBox.style.height = boxHeight * multiple + 'px';
showBox.style.position = 'fixed';
showBox.style.left = (mainL + mainW + 5) + 'px';
showBox.style.top = mainT + 'px';
showBox.style.overflow = 'hidden';
showBox.style.display = 'none';
showBox.style.zIndex = -999;
//创建图片
var showImg = document.createElement("img");
if (imgsrc == '') {
showImg.src = img.src;
} else {
showImg.src = imgsrc;
}

showImg.style.width = imgW * multiple + 'px';
showImg.style.height = imgH * multiple + 'px';
showImg.style.position = 'absolute';
//把图片添加到showBox内，
showBox.appendChild(showImg);
//再把showBox添加到body内
document.getElementsByTagName('body')[0].appendChild(showBox)

main.onmousemove = function(event) {
//获取鼠标位置
var x = event.pageX;
var y = event.pageY;

//把获取box的宽高放在显示之后才能获取到，若想在之前获取，用getComputedStyle(box).width
// var boxW = box.offsetWidth;
// var boxH = box.offsetHeight;

//对box的left和top进行赋值
//赋值前进行判断。让box不能超出main范围
var left = x – mainL – boxW / 2;
var top = y – mainT – boxH / 2;
if (left <= 0) {
left = 0;
}
if (top <= 0) {
top = 0;
}
if (left >= mainW – boxW) {
left = mainW – boxW;
}
if (top >= mainH – boxH) {
top = mainH – boxH;
}
box.style.left = left + 'px';
box.style.top = top + 'px';
//根据放大倍数设置showImg的位置
showImg.style.left = -left * multiple + 'px'
showImg.style.top = -top * multiple + 'px';
}
}