// Plugin (fade in - fade out)
(function($){
    var name_space = 'imgAnim';
    $.fn[name_space] = function(options) {
    
        var imgBox = this;
        var boxs = imgBox.find(".box");
        var boxs_count;
        var index = 1;
        
        var settings = $.extend({
            "anim"     : "slow"
           ,"interval" : "4000"
        }, options);
        
        var init = function(){
            num = 1;
            boxs.each(function(){
                $(this).find("a img").attr("class", "box" + num);// add class="box1" ...
                if( num > 1) $(this).find("a img").attr("class", "box" + num).hide();
                num++;
            });
            boxs_count = num - 1;
        };
        var fade = function(){
            $(".box" + index).fadeOut( settings["anim"], function(){
                index++;
                if( index > boxs_count) index = 1;
                $(".box" + index).fadeIn( settings["anim"], function(){
                    //alert("comp");
                });
            });
        };
        
        var timer = setInterval(function(){
            fade();
        }, settings["interval"]);
        
        //main
        init();
        
        //method chain
        return this;
    };
})(jQuery);