如何改变预加载功能?

时间:2012-05-24 16:36:20

标签: jquery image loading image-preloader

我需要有关我网站上的代码http://www.luischales.com/miami-quinces-photography.html的帮助。第一次打开它时,幻灯片不会启动,直到所有图像都被加载(我认为),客户不喜欢等待,所以我的问题是,有人能指出我按需加载图像的方法吗?或者至少加载第一批图像然后加载其他图像?

CODE

   //<![CDATA[
        $(function() {
            var $tf_bg              = $('#tf_bg'),
                $tf_bg_images       = $tf_bg.find('img'),
                $tf_bg_img          = $tf_bg_images.eq(0),
                $tf_thumbs          = $('#tf_thumbs'),
                total               = $tf_bg_images.length,
                current             = 0,
                $tf_content_wrapper = $('#tf_content_wrapper'),
                $tf_next            = $('#tf_next'),
                $tf_prev            = $('#tf_prev'),
                $tf_loading         = $('#tf_loading');

            //preload the images                
            $tf_bg_images.preload({
                onComplete  : function(){
                    $tf_loading.hide();
                    init();
                }
            });

            //shows the first image and initializes events
            function init(){
                //get dimentions for the image, based on the windows size
                var dim = getImageDim($tf_bg_img);
                //set the returned values and show the image
                $tf_bg_img.css({
                    width   : dim.width,
                    height  : dim.height,
                    left    : dim.left,
                    top     : dim.top
                }).fadeIn();

                //resizing the window resizes the $tf_bg_img
            $(window).bind('resize',function(){
                var dim = getImageDim($tf_bg_img);
                $tf_bg_img.css({
                    width   : dim.width,
                    height  : dim.height,
                    left    : dim.left,
                    top     : dim.top
                });
            });

                //expand and fit the image to the screen
                $('#tf_zoom').live('click',
                    function(){
                    if($tf_bg_img.is(':animated'))
                        return false;

                        var $this   = $(this);
                        if($this.hasClass('tf_zoom')){
                            resize($tf_bg_img);
                            $this.addClass('tf_fullscreen')
                                 .removeClass('tf_zoom');
                        }
                        else{
                            var dim = getImageDim($tf_bg_img);
                            $tf_bg_img.animate({
                                width   : dim.width,
                                height  : dim.height,
                                top     : dim.top,
                                left    : dim.left
                            },350);
                            $this.addClass('tf_zoom')
                                 .removeClass('tf_fullscreen'); 
                        }
                    }
                );

                //click the arrow down, scrolls down
                $tf_next.bind('click',function(){
                    if($tf_bg_img.is(':animated'))
                        return false;
                        scroll('tb');
                });

                //click the arrow up, scrolls up
                $tf_prev.bind('click',function(){
                    if($tf_bg_img.is(':animated'))
                    return false;
                    scroll('bt');
                });

                //mousewheel events - down / up button trigger the scroll down / up
                $(document).mousewheel(function(e, delta) {
                    if($tf_bg_img.is(':animated'))
                        return false;

                    if(delta > 0)
                        scroll('bt');
                    else
                        scroll('tb');
                    return false;
                });

                //key events - down / up button trigger the scroll down / up
                $(document).keydown(function(e){
                    if($tf_bg_img.is(':animated'))
                        return false;

                    switch(e.which){
                        case 38:    
                            scroll('bt');
                            break;  

                        case 40:    
                            scroll('tb');
                            break;
                    }
                });
            }

            //show next / prev image
            function scroll(dir){
                //if dir is "tb" (top -> bottom) increment current, 
                //else if "bt" decrement it
                current = (dir == 'tb')?current + 1:current - 1;

                //we want a circular slideshow, 
                //so we need to check the limits of current
                if(current == total) current = 0;
                else if(current < 0) current = total - 1;

                //flip the thumb
                $tf_thumbs.flip({
                    direction   : dir,
                    speed       : 400,
                    onBefore    : function(){
                        //the new thumb is set here
                        var content = '<span id="tf_zoom" class="tf_zoom"><\/span>';
                        content     +='<img src="' + $tf_bg_images.eq(current).attr('longdesc') + '" alt="Thumb' + (current+1) + '"/>';
                        $tf_thumbs.html(content);
                }
                });

                //we get the next image
                var $tf_bg_img_next = $tf_bg_images.eq(current),
                    //its dimentions
                    dim             = getImageDim($tf_bg_img_next),
                    //the top should be one that makes the image out of the viewport
                    //the image should be positioned up or down depending on the direction
                        top = (dir == 'tb')?$(window).height() + 'px':-parseFloat(dim.height,10) + 'px';

                //set the returned values and show the next image   
                    $tf_bg_img_next.css({
                        width   : dim.width,
                        height  : dim.height,
                        left    : dim.left,
                        top     : top
                    }).show();

                //now slide it to the viewport
                    $tf_bg_img_next.stop().animate({
                        top     : dim.top
                    },700);

                //we want the old image to slide in the same direction, out of the viewport
                    var slideTo = (dir == 'tb')?-$tf_bg_img.height() + 'px':$(window).height() + 'px';
                    $tf_bg_img.stop().animate({
                        top     : slideTo
                    },700,function(){
                    //hide it
                        $(this).hide();
                    //the $tf_bg_img is now the shown image
                        $tf_bg_img  = $tf_bg_img_next;
                    //show the description for the new image
                        $tf_content_wrapper.children()
                                           .eq(current)
                                           .show();
            });
                //hide the current description  
                    $tf_content_wrapper.children(':visible')
                                       .hide()

            }

            //animate the image to fit in the viewport
            function resize($img){
                var w_w = $(window).width(),
                    w_h = $(window).height(),
                    i_w = $img.width(),
                    i_h = $img.height(),
                    r_i = i_h / i_w,
                    new_w,new_h;

                if(i_w > i_h){
                    new_w   = w_w;
                    new_h   = w_w * r_i;

                    if(new_h > w_h){
                        new_h   = w_h;
                        new_w   = w_h / r_i;
                    }
                }   
                else{
                    new_h   = w_w * r_i;
                    new_w   = w_w;
                }

                $img.animate({
                    width   : new_w + 'px',
                    height  : new_h + 'px',
                    top     : '0px',
                    left    : '0px'
                },350);
            }

            //get dimentions of the image, 
            //in order to make it full size and centered
            function getImageDim($img){
                var w_w = $(window).width(),
                    w_h = $(window).height(),
                    r_w = w_h / w_w,
                    i_w = $img.width(),
                    i_h = $img.height(),
                    r_i = i_h / i_w,
                    new_w,new_h,
                    new_left,new_top;

                if(r_w > r_i){
                    new_h   = w_h;
                    new_w   = w_h / r_i;
                }
                else{
                    new_h   = w_w * r_i;
                    new_w   = w_w;
                }


                return {
                    width   : new_w + 'px',
                    height  : new_h + 'px',
                    left    : (w_w - new_w) / 2 + 'px',
                    top     : (w_h - new_h) / 2 + 'px'
                };
                }
        });
//]]>
</script>

1 个答案:

答案 0 :(得分:0)

您可以尝试从jQuery选择器中排除第一个图像:

$('.photos').not('.exclude-photo').preload();

另一个选项可能是此jQuery Image Preload Plugin,以查看API是否更符合您要完成的操作。