Jquery实现逐屏加载图片

引用jquery.scrollLoading.js

$(document).ready(function () {
            //实现图片慢慢浮现出来的效果
            $("img").load(function () {
                //图片默认隐藏  
                $(this).hide();
                //使用fadeIn特效  
                $(this).fadeIn("5000");
            });
            // 异步加载图片，实现逐屏加载图片
            $(".scrollLoading").scrollLoading(); 
});

//data-url表示将要异步加载的图片，src表示首先加载的图片
<img class="scrollLoading" data-url="image/logo.jpg" src="/Images/120.gif" />

 jquery.scrollLoading.js内容

(function ($) {
    // alert($.fn.scrollLoading);
    $.fn.scrollLoading = function (options) {
        var defaults = {
            attr: "data-url"
        };
        var params = $.extend({}, defaults, options || {});
        params.cache = [];
        $(this).each(function () {
            var node = this.nodeName.toLowerCase(), url = $(this).attr(params["attr"]);
            if (!url) { return; }
            var data = {
                obj: $(this),
                tag: node,
                url: url
            };
            params.cache.push(data);
        });

        var loading = function () {
            var st = $(window).scrollTop(), sth = st + $(window).height();
            $.each(params.cache, function (i, data) {
                var o = data.obj, tag = data.tag, url = data.url;
                if (o) {
                    post = o.position().top; posb = post + o.height();
                    if ((post > st && post < sth) || (posb > st && posb < sth)) {
                        if (tag === "img") {
                            o.attr("src", url);
                        } else {
                            o.load(url);
                        }
                        data.obj = null;
                    }
                }
            });
            return false;
        };

        loading();
        $(window).bind("scroll", loading);
    };
})(jQuery);