图片放大镜js特效

今天看js教程,做了一个js放大镜效果,小小的开心了一把.下面为js源码:
View Code
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>放大镜效果</title>
    <style type="text/css">
        #div1
        {
            width: 200px;
            height: 150px;
            padding: 5px;
            border: 1px solid #ccc;
            position: relative;
        }

            #div1 .small_Pic
            {
                width: 200px;
                height: 150px;
                background: #eee;
                position: relative;
            }

            #div1 .float_layer
            {
                width: 50px;
                height: 50px;
                border: 1px solid #000;
                background: #fff;
                filter: alpha(opacity=30);
                opacity: 0.3;
                position: absolute;
                top: 0;
                left: 0;
                display: none;
            }

            #div1 .mark
            {
                width: 100%;
                height: 100%;
                position: absolute;
                z-index: 2;
                left: 0px;
                top: 0px;
                background: red;
                filter: alpha(opacity=0);
                opacity: 0;
            }

            #div1 .big_Pic
            {
                position: absolute;
                top: -1px;
                left: 315px;
                width: 200px;
                height: 235px;
                overflow: hidden;
                border: 2px solid #ccc;
                display: none;
            }

                #div1 .big_Pic img
                {
                    position: absolute;
                    top: 0px;
                    left: 0px;
                }
    </style>
    <script type="text/javascript">
        window.onload = function () {
            var oDiv = document.getElementById("div1");
            var oMark = getByClass(oDiv, 'mark')[0];
            var oFloat = getByClass(oDiv, 'float_layer')[0];
            var oBig = getByClass(oDiv, 'big_Pic')[0];
            var oSmall = getByClass(oDiv, 'small_Pic')[0];
            var oImg = oBig.getElementsByTagName('img')[0];
            oMark.onmouseover = function () {
                oFloat.style.display = 'block';
                oBig.style.display = 'block';

            }
            oMark.onmouseout = function () {
                oFloat.style.display = 'none';
                oBig.style.display = 'none';
            }
            oMark.onmousemove = function (ev) {
                var oEvent = ev || event;
                var l = oEvent.clientX - oSmall.offsetLeft - oDiv.offsetLeft - oFloat.offsetWidth / 2;
                var t = oEvent.clientY - oSmall.offsetTop - oDiv.offsetTop - oFloat.offsetHeight / 2;
                if (l < 0) {
                    l = 0;
                }
                else if (l > oMark.offsetWidth - oFloat.offsetWidth) {
                    l = oMark.offsetWidth - oFloat.offsetWidth;
                }
                if (t < 0) {
                    t = 0;
                }
                else if (t > oMark.offsetHeight - oFloat.offsetHeight) {
                    t = oMark.offsetHeight - oFloat.offsetHeight;
                }
                oFloat.style.left = l + "px";
                oFloat.style.top = t + "px";

                var percentX = l / (oMark.offsetWidth - oFloat.offsetWidth) * (oImg.offsetWidth - oBig.offsetWidth);

                var percentY = t / (oMark.offsetHeight - oFloat.offsetHeight) * (oImg.offsetHeight - oBig.offsetHeight);

                oImg.style.left = -percentX + "px";

                oImg.style.top = -percentY + "px";
            }
        }
        //根据class获取元素
        function getByClass(oParent, sClass) {
            var aEle = oParent.getElementsByTagName('*');
            var aTemp = [];
            for (var i = 0; i < aEle.length; i++) {
                if (aEle[i].className == sClass) {
                    aTemp.push(aEle[i]);
                }
            }
            return aTemp;
        }
    </script>
</head>
<body>
    <div id="div1">
        <div class="small_Pic">
            <span class="mark"></span>
            <span class="float_layer"></span>
            <img src="http://pic002.cnblogs.com/images/2012/297868/2012060918344911.jpg" alt="小图" />
        </div>
        <div class="big_Pic">
            <img src="http://pic002.cnblogs.com/images/2012/297868/2012060918343324.jpg" alt="大图" />
        </div>
    </div>
</body>
</html>