$.extend({
    imgLazyLoad: function(options) {
        var config = {
                container: 'body',
                tabItemSelector: '',
                carouselItemSelector: '',
                attrName: 'imglazyload-src',
                diff: 0
            };
        $.extend( config, options 
 
|| {} );

        var $container = $(config.container),
            offsetObj = $container.offset(),
            compareH = $(window).height() + $(window).scrollTop(),

            // 判斷容器是否為body子元素
            bl = $.contains( document.body, $container.get(0) ),

            // 過濾快取容器中的圖片
            notImgSelector = jQuery.imgLazyLoad.selectorCache ? ':not(' + jQuery.imgLazyLoad.selectorCache + ')' : '',
            imgSelector 
 
= 'img[' + config.attrName + ']:visible' + notImgSelector,
            $filterImgs = $container.find(imgSelector),

            // 用於阻止事件處理
            isStopEventHandle = false,
            
            // 是否自動懶載入，為true時，繫結滾動事件
            isAutoLazyload = false;

        // 快取容器為body子元素的圖片選擇器
        jQuery.imgLazyLoad.selectorCache = bl ? (jQuery.imgLazyLoad.selectorCache ? (jQuery.imgLazyLoad.selectorCache + ',' + config.container + ' img') : config.container + ' img') : jQuery.imgLazyLoad.selectorCache;

        
 
function handleImgLoad(idx) {
            if (isStopEventHandle) {
                return;
            }
            /**
             處理Tab切換，圖片輪播，在處理$filterImgs時，沒有過濾img:not(.img-loaded)，因為只是在一個面板中，
             還有其他面板，如果再次觸發，可能$filterImgs.length為0，因此只能在外圍容器中判斷過濾圖片length
            */            
            if ($container.find('img:not(.img-loaded)').length === 0) {
                isStopEventHandle = true;
            }

            var itemSelector = config.tabItemSelector || config.carouselItemSelector || '';
            if (itemSelector) {
                if (typeof idx !== undefined && idx >= 0) {
                    $filterImgs = $container.find(itemSelector).eq(idx).find('img');
                }
                else {
                    if (itemSelector === config.carouselItemSelector) {
                        $filterImgs = $container.find(itemSelector).eq(0).find('img');
                    }
                    else {
                        $filterImgs = $container.find(itemSelector + ':visible').find('img');
                    }
                }
            }
            else {
                $filterImgs = $filterImgs.not('.img-loaded'); // 自動懶載入，過濾已載入的圖片
                isAutoLazyload = true;
            }

            // 當外圍容器位置發生變化，需更新
            offsetObj = $container.offset();

            if ($filterImgs.length > 0) {
                $filterImgs.each(function(idx, elem) {
                    var $target = $(elem),
                        targetTop = $target.offset().top,
                        viewH = $(window).height() + $(window).scrollTop() + config.diff;

                    if (bl) {
                        $target.attr('src', $target.attr(config.attrName)).removeAttr(config.attrName).addClass('img-loaded');
                    }
                    // 內容在視窗中
                    if (viewH > targetTop) {
                        $target.attr('src', $target.attr(config.attrName)).removeAttr(config.attrName).addClass('img-loaded');
                    }
                });
            }
            else {
                // 處理滾動事件
                isStopEventHandle = true;
                $(window).unbind('resize scroll', handleImgLoad);
            }
        }

        handleImgLoad();
        if (isAutoLazyload) {
            $(window).bind('resize scroll', handleImgLoad);
        }

        // 提供事件處理函式
        return {
            handleImgLoad: handleImgLoad
        }
    }
});

// 儲存非body子元素容器下的圖片選擇器
jQuery.imgLazyLoad.selectorCache = '';