第一次自己写jquery图片延迟加载插件，不通用，但修改一下还是可以使用到很多页面上的

/*!
* jquery.lazyoading.js
*自定义的页面图片延迟加载插件，比网上的jquery.lazyload简单，也更适合自己的网站
*使用方法：
把img 的class加上 lazyloading
然后先引用jquery，再引用jquery.lazyoading.js，再调用：$("img.lazyloading").lazyloading({loadfirst:true});
* by pukuimin
* 2013-11-01
*2013-11-08 解决了图片没有指定高度的问题
*2013-11-14 解决了没有指定高度加载图片之后有间隔的问题
*/
/// <reference path="jquery-1.8.2.min.js" />
(function ($) {
$.fn.lazyloading = function (options) {
var defaults = {
preyimg: "/Content/images/Imgpreview/grey.gif",
picpath: "data-original",
container: $(window),
loadfirst: false, //进入页面后是否加载当前页面的图片
defaultHeightID: "lazyloadingHeight"//页面上默认高度的input标签id
//imgPaddingID: "lazyloadingPadding"//img的padding值
};
var params = $.extend({}, defaults, options || {});
params.cache = [];
$(this).each(function () {
var node = this.nodeName.toLowerCase(), url = $(this).attr(params["picpath"]), preyimg = params["preyimg"];
var defaultheight = $("#" + params["defaultHeightID"]).val(); //, padding = $("#" + params["imgPaddingID"]).val(); //
//重组
var data = {
obj: $(this),
tag: node,
url: url,
preyimg: preyimg,
defaultheight: defaultheight
};
params.cache.push(data);
});

var init = function () {
$.each(params.cache, function (i, data) {
var thisImg = data.obj, tag = data.tag, url = data.url, preyimg = data.preyimg;
if (typeof (url) != "undefined")// 判断是否需要延迟加载
{
var parent1 = thisImg.parent(); //a
var Inner = null; //
if (parent1.is("a") == true) {//img wrap by a
Inner = parent1;
}
else {
Inner = thisImg;
}
var width = thisImg.attr("width") || thisImg.css("width");
var height = data.defaultheight || thisImg.css("height");
//if (i == 0) alert(data.defaultheight);
var attrheight = thisImg.attr("height");
if (attrheight != null) height = attrheight;
if (width != null && width.indexOf("px") > -1) width.replace("px", "");
if (height != null && height.indexOf("px") > -1) height.replace("px", "");
var divstr = "<div class='.loading' style='text-align: left;position:relative;float:left;width:" + width + "px;";
var HasHeight = true; //图片是否指定了高度
divstr = divstr + "height:" + height + "px;";
if (attrheight == null || attrheight == "") {
HasHeight = false;
}

thisImg.css("position", "relative");

divstr = divstr + "' ></div>"
//修正外层div：text-align的影响
Inner.wrap(divstr);
//修正img外面不是a标签时parent()已经改变的问题
parent1 = thisImg.parent();
if (HasHeight == true) { parent1.attr("lazyloading_hasheight", "1"); } //是否指定了高度
else { { parent1.attr("lazyloading_hasheight", "0"); } }

parent1.append("<img class='loadhiddenimg' width='0' height='0' src='' />");
thisImg.attr("src", preyimg);
thisImg.removeAttr("width").removeAttr("height");
thisImg.attr("width1", width).attr("height1", attrheight);

////thisImg.attr("width", "50px").attr("height", "50px"); //loading图大小
//thisImg.css("margin", "0 auto");
thisImg.css("margin", ((height / 2) - 25) + "px auto auto " + ((width / 2) - 25) + "px");
$(".lazyloading").css("display", "table"); //.css("position", "relative");
}
});
}
//动态显示数据
var loading = function () {
//窗口的高度+看不见的顶部的高度=屏幕低部距离最顶部的高度
var thisButtomTop = parseInt($(window).height()) + parseInt($(window).scrollTop());
var thisTop = parseInt($(window).scrollTop()); //屏幕顶部距离最顶部的高度

$.each(params.cache, function (i, data) {
var thisImg = data.obj, tag = data.tag, url = data.url, post, posb;

if (thisImg) {//对象不为空
if (typeof (url) != "undefined") {// 判断是否需要延迟加载
var PictureTop = parseInt(thisImg.offset().top);
//如果处理可见范围内，并且原图地址data-original不等于src,则加载图片
if (PictureTop >= thisTop && PictureTop <= thisButtomTop && thisImg.attr("data-original") != thisImg.attr("src")) {
var hiddenImg = thisImg.siblings("img.loadhiddenimg");

hiddenImg.load(function () { //隐藏图片加载完之后的回调函数
var width = thisImg.attr("width1");
var height = thisImg.attr("height1");
thisImg.attr("width", width).attr("height", height);
thisImg.removeAttr("width1").removeAttr("height1");
thisImg.css("margin", "0 auto");
if (thisImg.parent().attr("lazyloading_hasheight") == "0") {//没有指定高度时，加载图片后去掉div高度自适应
if (thisImg.parent().is("a") == true) {
thisImg.parent().parent().css("height", "");
}
else {
thisImg.parent().css("height", "");
}
}
thisImg.load(function () {
if (thisImg.parent().is("a") == true) {
thisImg.parent().parent().css("height", thisImg.height());
}
else {
thisImg.parent().css("height", thisImg.height());
}
});
thisImg.attr("src", hiddenImg.attr("src"));
}).error(function () {
thisImg.attr("src", hiddenImg.attr("src")); //alert("error");
});
hiddenImg.attr("src", url);
}
}
}
});
};
//初始化
init();
//事件触发
//加载完毕即执行
if (params["loadfirst"] == true) loading();
//滚动执行
params.container.bind("scroll", loading).bind("resize", loading);
};
})(jQuery);