图片延迟加载JQuery插件jquery-image-lazy-loading

使用该插件将页面中的图片进行延迟加载，当需要显示该图片的时候才导入显示图片，提高页面加载速度。

jquery.lazyload.js

源代码:

/*

 * Lazy Load - jQuery plugin for lazy loading images

 *

 * Copyright (c) 2007-2011 Mika Tuupola

 *

 * Licensed under the MIT license:

 *   http://www.opensource.org/licenses/mit-license.php

 *

 * Project home:

 *   http://www.appelsiini.net/projects/lazyload

 *

 * Version:  1.7.0-dev

 *

 */

(function($) {

    $.fn.lazyload = function(options) {

        var settings = {

            threshold       : 0,

            failure_limit   : 0,

            event           : "scroll",

            effect          : "show",

            container       : window,

            skip_invisible  : true

        };

                

        if(options) {

            /* Maintain BC for a couple of version. */

            if (undefined !== options.failurelimit) {

                options.failure_limit = options.failurelimit; 

                delete options.failurelimit;

            }

            

            $.extend(settings, options);

        }

        /* Fire one scroll event per scroll. Not one scroll event per image. */

        var elements = this;

        if (0 == settings.event.indexOf("scroll")) {

            $(settings.container).bind(settings.event, function(event) {

                var counter = 0;

                elements.each(function() {

                    if (settings.skip_invisible && !$(this).is(":visible")) return;

                    if ($.abovethetop(this, settings) ||

                        $.leftofbegin(this, settings)) {

                            /* Nothing. */

                    } else if (!$.belowthefold(this, settings) &&

                        !$.rightoffold(this, settings)) {

                            $(this).trigger("appear");

                    } else {

                        if (++counter > settings.failure_limit) {

                            return false;

                        }

                    }

                });

                /* Remove image from array so it is not looped next time. */

                var temp = $.grep(elements, function(element) {

                    return !element.loaded;

                });

                elements = $(temp);

            });

        }

        

        this.each(function() {

            var self = this;            

            self.loaded = false;

            

            /* When appear is triggered load original image. */

            $(self).one("appear", function() {

                if (!this.loaded) {

                    $("<img />")

                        .bind("load", function() {

                            $(self)

                                .hide()

                                .attr("src", $(self).data("original"))

                                [settings.effect](settings.effectspeed);

                            self.loaded = true;

                        })

                        .attr("src", $(self).data("original"));

                };

            });

            /* When wanted event is triggered load original image */

            /* by triggering appear.                              */

            if (0 != settings.event.indexOf("scroll")) {

                $(self).bind(settings.event, function(event) {

                    if (!self.loaded) {

                        $(self).trigger("appear");

                    }

                });

            }

        });

        

        /* Check if something appears when window is resized. */

        $(window).bind("resize", function(event) {

            $(settings.container).trigger(settings.event);

        });

        

        /* Force initial check if images should appear. */

        $(settings.container).trigger(settings.event);

        

        return this;

    };

    /* Convenience methods in jQuery namespace.           */

    /* Use as  $.belowthefold(element, {threshold : 100, container : window}) */

    $.belowthefold = function(element, settings) {

        if (settings.container === undefined || settings.container === window) {

            var fold = $(window).height() + $(window).scrollTop();

        } else {

            var fold = $(settings.container).offset().top + $(settings.container).height();

        }

        return fold <= $(element).offset().top - settings.threshold;

    };

    

    $.rightoffold = function(element, settings) {

        if (settings.container === undefined || settings.container === window) {

            var fold = $(window).width() + $(window).scrollLeft();

        } else {

            var fold = $(settings.container).offset().left + $(settings.container).width();

        }

        return fold <= $(element).offset().left - settings.threshold;

    };

        

    $.abovethetop = function(element, settings) {

        if (settings.container === undefined || settings.container === window) {

            var fold = $(window).scrollTop();

        } else {

            var fold = $(settings.container).offset().top;

        }

        return fold >= $(element).offset().top + settings.threshold  + $(element).height();

    };

    

    $.leftofbegin = function(element, settings) {

        if (settings.container === undefined || settings.container === window) {

            var fold = $(window).scrollLeft();

        } else {

            var fold = $(settings.container).offset().left;

        }

        return fold >= $(element).offset().left + settings.threshold + $(element).width();

    };

    /* Custom selectors for your convenience.   */

    /* Use as $("img:below-the-fold").something() */

    $.extend($.expr[':'], {

        "below-the-fold" : function(a) { return $.belowthefold(a, {threshold : 0, container: window}) },

        "above-the-fold" : function(a) { return !$.belowthefold(a, {threshold : 0, container: window}) },

        "right-of-fold"  : function(a) { return $.rightoffold(a, {threshold : 0, container: window}) },

        "left-of-fold"   : function(a) { return !$.rightoffold(a, {threshold : 0, container: window}) }

    });

    

})(jQuery);

下载地址：

https://github.com/tuupola/jquery_lazyload

使用方法:

$("#meisgMarquee img").lazyload({placeholder : "/css/vcode.jpg",effect : "fadeIn"});

更多介绍见;

http://www.appelsiini.net/projects/lazyload