;(function($){$.fn.extend({scrollLoad:function(options){var options = $.extend({src:'xsrc',  //预加载在<img> 中的属性值  如<img xsrc='img.jpg' />delayTime:300 // 滚动条停止在一个地方超过300毫秒，才开始加载
                },options);var _this = this; //将this保存下来。
            init.call(_this); //页面载入后马上加载一次。
            $(window).scroll(function(){ //给窗口绑定事件，当滚动条滚动时，加载图片window.setTimeout(function(){init.call(_this);    },options.delayTime);    });function init(){$(this).each(function(i,n){if(n.tagName.toLowerCase() !=='img'){return;    }if($(n).attr(options.src) === 'undefined'){return;    }var windowTop = $(document).scrollTop(),windowBottom = windowTop + $(window).height(),imgTop = $(n).offset().top,imgBottom = imgTop + $(n).height();if(imgBottom>windowTop && imgTop<windowBottom){$(n).attr('src',$(n).attr(options.src)).removeAttr(options.src);}});};}});})(jQuery);

<script type="text/javascript" src="jquery-1.8.2.min.js"></script>
<script type="text/javascript" src="scrollLoad/jquery.scrollLoad.js"></script>

$('img').scrollLoad();

{src:'xsrc',  //预加载在<img> 中的属性值  如<img xsrc='img.jpg' />delayTime:300 // 滚动条停止在一个地方超过300毫秒，才开始加载}

  var scrollLoad = (function (options) {var defaults = (arguments.length == 0) ? { src: 'xSrc', time: 300} : { src: options.src || 'xSrc', time: options.time ||300};var camelize = function (s) {return s.replace(/-(\w)/g, function (strMatch, p1) {return p1.toUpperCase();});};this.getStyle = function (element, property) {if (arguments.length != 2) return false;var value = element.style[camelize(property)];if (!value) {if (document.defaultView && document.defaultView.getComputedStyle) {var css = document.defaultView.getComputedStyle(element, null);value = css ? css.getPropertyValue(property) : null;} else if (element.currentStyle) {value = element.currentStyle[camelize(property)];}}return value == 'auto' ? '' : value;};var _init = function () {// offsetPage 页面滚动条的为止 即页面页面可视区域顶端距离整个文档上方距离// offsetWindow offsetPage+页面可视区域的高度 可视区域底部距离文档上方距离var offsetPage = window.pageYOffset ? window.pageYOffset : window.document.documentElement.scrollTop,offsetWindow = offsetPage + Number(window.innerHeight ? window.innerHeight : document.documentElement.clientHeight),docImg = document.images,_len = docImg.length;if (!_len) return false;for (var i = 0; i < _len; i++) {var attrSrc = docImg[i].getAttribute(defaults.src),o = docImg[i], tag = o.nodeName.toLowerCase();if (o) {//获取图像顶部距离整个页面的距离postPage = o.getBoundingClientRect().top + window.document.documentElement.scrollTop + window.document.body.scrollTop; postWindow = postPage + Number(this.getStyle(o, 'height').replace('px', ''));//获取图像底部距离整个页面的距离//如果图像上方在屏幕可视区域中间  或者 图像下方在屏幕区域if ((postPage > offsetPage && postPage < offsetWindow) || (postWindow > offsetPage && postWindow < offsetWindow)) {if (tag === "img" && attrSrc !== null) {o.setAttribute("src", attrSrc);}o = null;}}};window.onscroll = function () {setTimeout(function () {_init();}, defaults.time);}};return _init();//返回初始化函数});