图片设置上一页、下一页、切换、预加载等功能：

//相册层
    layer.photos = function(options, loop, key){
        var dict = {};
        options = options || {};
        if(!options.photos) return;
        var type = options.json || options.photos.constructor === Object;
        var photos = type ? options.photos : {}, data = photos.data || [];
        var start = photos.start || 0;
        dict.imgIndex = (start|0) + 1;

        options.img = options.img || 'img';

        var success = options.success;
        delete options.success;

        if(!type){ //页面直接获取
            var parent = $(options.photos), pushData = function(){
                data = [];
                parent.find(options.img).each(function(index){
                    var othis = $(this);
                    othis.attr('layer-index', index);
                    data.push({
                        alt: othis.attr('alt'),
                        pid: othis.attr('layer-pid'),
                        src: othis.attr('layer-src') || othis.attr('src'),
                        thumb: othis.attr('src')
                    });
                })
            };

            pushData();

            if (data.length === 0) return;

            loop || parent.off("click").on('click', options.img, function(){
                var othis = $(this), index = othis.attr('layer-index');
                layer.photos($.extend(options, {
                    photos: {
                        start: index,
                        data: data,
                        tab: options.tab
                    },
                    full: options.full
                }), true);
                pushData();
            })

            //不直接弹出
            if(!loop) return;

        } else if (data.length === 0){
            return layer.msg('没有图片');
        }

        //上一张
        dict.imgprev = function(key){
            dict.imgIndex--;
            if(dict.imgIndex < 1){
                dict.imgIndex = data.length;
            }
            dict.tabimg(key);
        };

        //下一张
        dict.imgnext = function(key,errorMsg){
            dict.imgIndex++;
            if(dict.imgIndex > data.length){
                dict.imgIndex = 1;
                if (errorMsg) {return};
            }
            dict.tabimg(key)
        };

        //方向键
        dict.keyup = function(event){
            if(!dict.end){
                var code = event.keyCode;
                event.preventDefault();
                if(code === 37){
                    dict.imgprev(true);
                } else if(code === 39) {
                    dict.imgnext(true);
                } else if(code === 27) {
                    layer.close(dict.index);
                }
            }
        }

        //切换
        dict.tabimg = function(key){
            if(data.length <= 1) return;
            photos.start = dict.imgIndex - 1;
            layer.close(dict.index);
            return layer.photos(options, true, key);
            setTimeout(function(){
            layer.photos(options, true, key);
            }, 200);
        }

        //一些动作
        dict.event = function(){
            dict.bigimg.hover(function(){
                dict.imgsee.show();
            }, function(){
                dict.imgsee.hide();
            });

            dict.bigimg.find('.layui-layer-imgprev').on('click', function(event){
                event.preventDefault();
                dict.imgprev();
            });

            dict.bigimg.find('.layui-layer-imgnext').on('click', function(event){
                event.preventDefault();
                dict.imgnext();
            });

            $(document).on('keyup', dict.keyup);
        };

        //图片预加载
        function loadImage(url, callback, error) {
            var img = new Image();
            img.src = url;
            if(img.complete){
                return callback(img);
            }
            img.onload = function(){
                img.onload = null;
                callback(img);
            };
            img.onerror = function(e){
                img.onerror = null;
                error(e);
            };
        };

        dict.loadi = layer.load(1, {
            shade: 'shade' in options ? false : 0.9,
            scrollbar: false
        });
        loadImage(data[start].src, function(img){
            layer.close(dict.loadi);
            dict.index = layer.open($.extend({
                type: 1,
                id: 'layui-layer-photos',
                area: function(){
                    var imgarea = [img.width, img.height];
                    var winarea = [$(window).width() - 100, $(window).height() - 100];

                    //如果 实际图片的宽或者高比 屏幕大（那么进行缩放）
                    if(!options.full && (imgarea[0]>winarea[0]||imgarea[1]>winarea[1])){
                        var wh = [imgarea[0]/winarea[0],imgarea[1]/winarea[1]];//取宽度缩放比例、高度缩放比例
                        if(wh[0] > wh[1]){//取缩放比例最大的进行缩放
                            imgarea[0] = imgarea[0]/wh[0];
                            imgarea[1] = imgarea[1]/wh[0];
                        } else if(wh[0] < wh[1]){
                            imgarea[0] = imgarea[0]/wh[1];
                            imgarea[1] = imgarea[1]/wh[1];
                        }
                    }

                    return [imgarea[0]+'px', imgarea[1]+'px'];
                }(),
                title: false,
                shade: 0.9,
                shadeClose: true,
                closeBtn: false,
                move: '.layui-layer-phimg img',
                moveType: 1,
                scrollbar: false,
                moveOut: true,
                //anim: Math.random()*5|0,
                isOutAnim: false,
                skin: 'layui-layer-photos' + skin('photos'),
                content: '<div class="layui-layer-phimg">'
                +'<img src="'+ data[start].src +'" alt="'+ (data[start].alt||'') +'" layer-pid="'+ data[start].pid +'">'
                +'<div class="layui-layer-imgsee">'
                +(data.length > 1 ? '<span class="layui-layer-imguide"><a href="javascript:;" class="layui-layer-iconext layui-layer-imgprev"></a><a href="javascript:;" class="layui-layer-iconext layui-layer-imgnext"></a></span>' : '')
                +'<div class="layui-layer-imgbar" style="display:'+ (key ? 'block' : '') +'"><span class="layui-layer-imgtit"><a href="javascript:;">'+ (data[start].alt||'') +'</a><em>'+ dict.imgIndex +'/'+ data.length +'</em></span></div>'
                +'</div>'
                +'</div>',
                success: function(layero, index){
                    dict.bigimg = layero.find('.layui-layer-phimg');
                    dict.imgsee = layero.find('.layui-layer-imguide,.layui-layer-imgbar');
                    dict.event(layero);
                    options.tab && options.tab(data[start], layero);
                    typeof success === 'function' && success(layero);
                }, end: function(){
                    dict.end = true;
                    $(document).off('keyup', dict.keyup);
                }
            }, options));
        }, function(){
            layer.close(dict.loadi);
            layer.msg('&#x5F53;&#x524D;&#x56FE;&#x7247;&#x5730;&#x5740;&#x5F02;&#x5E38;<br>&#x662F;&#x5426;&#x7EE7;&#x7EED;&#x67E5;&#x770B;&#x4E0B;&#x4E00;&#x5F20;&#xFF1F;', {
                time: 30000,
                btn: ['&#x4E0B;&#x4E00;&#x5F20;', '&#x4E0D;&#x770B;&#x4E86;'],
                yes: function(){
                    data.length > 1 && dict.imgnext(true,true);
                }
            });
        });
    };