提高Baidu Map聚合的效率

　　百度的MAP的例子里提供了一个聚合效果，地址是http://developer.baidu.com/map/jsdemo.htm#c1_4 ，效果图如下图：

　　

　　这个效果很赞，但效率很低，当数据量达到5000的时候就难以忍受了，加载和地图缩放都很卡，用户体验很差劲。官方提供的MarkerClusterer.js 文件是这样的：

/**
 * @fileoverview MarkerClusterer标记聚合器用来解决加载大量点要素到地图上产生覆盖现象的问题，并提高性能。
 * 主入口类是<a href="symbols/BMapLib.MarkerClusterer.html">MarkerClusterer</a>，
 * 基于Baidu Map API 1.2。
 *
 * @author Baidu Map Api Group
 * @version 1.2
 */

/**
 * @namespace BMap的所有library类均放在BMapLib命名空间下
 */
var BMapLib = window.BMapLib = BMapLib || {};
(function(){

    /**
     * 获取一个扩展的视图范围，把上下左右都扩大一样的像素值。
     * @param {Map} map BMap.Map的实例化对象
     * @param {BMap.Bounds} bounds BMap.Bounds的实例化对象
     * @param {Number} gridSize 要扩大的像素值
     *
     * @return {BMap.Bounds} 返回扩大后的视图范围。
     */
    var getExtendedBounds = function(map, bounds, gridSize){
        bounds = cutBoundsInRange(bounds);
        var pixelNE = map.pointToPixel(bounds.getNorthEast());
        var pixelSW = map.pointToPixel(bounds.getSouthWest());
        pixelNE.x += gridSize;
        pixelNE.y -= gridSize;
        pixelSW.x -= gridSize;
        pixelSW.y += gridSize;
        var newNE = map.pixelToPoint(pixelNE);
        var newSW = map.pixelToPoint(pixelSW);
        return new BMap.Bounds(newSW, newNE);
    };

    /**
     * 按照百度地图支持的世界范围对bounds进行边界处理
     * @param {BMap.Bounds} bounds BMap.Bounds的实例化对象
     *
     * @return {BMap.Bounds} 返回不越界的视图范围
     */
    var cutBoundsInRange = function (bounds) {
        var maxX = getRange(bounds.getNorthEast().lng, -180, 180);
        var minX = getRange(bounds.getSouthWest().lng, -180, 180);
        var maxY = getRange(bounds.getNorthEast().lat, -74, 74);
        var minY = getRange(bounds.getSouthWest().lat, -74, 74);
        return new BMap.Bounds(new BMap.Point(minX, minY), new BMap.Point(maxX, maxY));
    }; 

    /**
     * 对单个值进行边界处理。
     * @param {Number} i 要处理的数值
     * @param {Number} min 下边界值
     * @param {Number} max 上边界值
     *
     * @return {Number} 返回不越界的数值
     */
    var getRange = function (i, mix, max) {
        mix && (i = Math.max(i, mix));
        max && (i = Math.min(i, max));
        return i;
    };

    /**
     * 判断给定的对象是否为数组
     * @param {Object} source 要测试的对象
     *
     * @return {Boolean} 如果是数组返回true，否则返回false
     */
    var isArray = function (source) {
        return '[object Array]' === Object.prototype.toString.call(source);
    };

    /**
     * 返回item在source中的索引位置
     * @param {Object} item 要测试的对象
     * @param {Array} source 数组
     *
     * @return {Number} 如果在数组内，返回索引，否则返回-1
     */
    var indexOf = function(item, source){
        var index = -1;
        if(isArray(source)){
            if (source.indexOf) {
                index = source.indexOf(item);
            } else {
                for (var i = 0, m; m = source[i]; i++) {
                    if (m === item) {
                        index = i;
                        break;
                    }
                }
            }
        }
        return index;
    };

    /**
     *@exports MarkerClusterer as BMapLib.MarkerClusterer
     */
    var MarkerClusterer =
        /**
         * MarkerClusterer
         * @class 用来解决加载大量点要素到地图上产生覆盖现象的问题，并提高性能
         * @constructor
         * @param {Map} map 地图的一个实例。
         * @param {Json Object} options 可选参数，可选项包括：<br />
         *    markers {Array<Marker>} 要聚合的标记数组<br />
         *    girdSize {Number} 聚合计算时网格的像素大小，默认60<br />
         *    maxZoom {Number} 最大的聚合级别，大于该级别就不进行相应的聚合<br />
         *    minClusterSize {Number} 最小的聚合数量，小于该数量的不能成为一个聚合，默认为2<br />
         *    isAverangeCenter {Boolean} 聚合点的落脚位置是否是所有聚合在内点的平均值，默认为否，落脚在聚合内的第一个点<br />
         *    styles {Array<IconStyle>} 自定义聚合后的图标风格，请参考TextIconOverlay类<br />
         */
        BMapLib.MarkerClusterer = function(map, options){
            if (!map){
                return;
            }
            this._map = map;
            this._markers = [];
            this._clusters = [];

            var opts = options || {};
            this._gridSize = opts["gridSize"] || 60;
            this._maxZoom = opts["maxZoom"] || 18;
            this._minClusterSize = opts["minClusterSize"] || 2;
            this._isAverageCenter = false;
            if (opts['isAverageCenter'] != undefined) {
                this._isAverageCenter = opts['isAverageCenter'];
            }
            this._styles = opts["styles"] || [];

            var that = this;
            this._map.addEventListener("zoomend",function(){
                that._redraw();
            });

            this._map.addEventListener("moveend",function(){
                 that._redraw();
            });

            var mkrs = opts["markers"];
            isArray(mkrs) && this.addMarkers(mkrs);
        };

    /**
     * 添加要聚合的标记数组。
     * @param {Array<Marker>} markers 要聚合的标记数组
     *
     * @return 无返回值。
     */
    MarkerClusterer.prototype.addMarkers = function(markers){
        for(var i = 0, len = markers.length; i <len ; i++){
            this._pushMarkerTo(markers[i]);
        }
        this._createClusters();
    };

    /**
     * 把一个标记添加到要聚合的标记数组中
     * @param {BMap.Marker} marker 要添加的标记
     *
     * @return 无返回值。
     */
    MarkerClusterer.prototype._pushMarkerTo = function(marker){
        var index = indexOf(marker, this._markers);
        if(index === -1){
            marker.isInCluster = false;
            this._markers.push(marker);//Marker拖放后enableDragging不做变化，忽略
        }
    };

    /**
     * 添加一个聚合的标记。
     * @param {BMap.Marker} marker 要聚合的单个标记。
     * @return 无返回值。
     */
    MarkerClusterer.prototype.addMarker = function(marker) {
        this._pushMarkerTo(marker);
        this._createClusters();
    };

    /**
     * 根据所给定的标记，创建聚合点
     * @return 无返回值
     */
    MarkerClusterer.prototype._createClusters = function(){
        var mapBounds = this._map.getBounds();
        var extendedBounds = getExtendedBounds(this._map, mapBounds, this._gridSize);
        for(var i = 0, marker; marker = this._markers[i]; i++){
            if(!marker.isInCluster && extendedBounds.containsPoint(marker.getPosition()) ){
                this._addToClosestCluster(marker);
            }
        }
    };

    /**
     * 根据标记的位置，把它添加到最近的聚合中
     * @param {BMap.Marker} marker 要进行聚合的单个标记
     *
     * @return 无返回值。
     */
    MarkerClusterer.prototype._addToClosestCluster = function (marker){
        var distance = 4000000;
        var clusterToAddTo = null;
        var position = marker.getPosition();
        for(var i = 0, cluster; cluster = this._clusters[i]; i++){
            var center = cluster.getCenter();
            if(center){
                var d = this._map.getDistance(center, marker.getPosition());
                if(d < distance){
                    distance = d;
                    clusterToAddTo = cluster;
                }
            }
        }

        if (clusterToAddTo && clusterToAddTo.isMarkerInClusterBounds(marker)){
            clusterToAddTo.addMarker(marker);
        } else {
            var cluster = new Cluster(this);
            cluster.addMarker(marker);
            this._clusters.push(cluster);
        }
    };

    /**
     * 清除上一次的聚合的结果
     * @return 无返回值。
     */
    MarkerClusterer.prototype._clearLastClusters = function(){
        for(var i = 0, cluster; cluster = this._clusters[i]; i++){
            cluster.remove();
        }
        this._clusters = [];//置空Cluster数组
        this._removeMarkersFromCluster();//把Marker的cluster标记设为false
    };

    /**
     * 清除某个聚合中的所有标记
     * @return 无返回值
     */
    MarkerClusterer.prototype._removeMarkersFromCluster = function(){
        for(var i = 0, marker; marker = this._markers[i]; i++){
            marker.isInCluster = false;
        }
    };

    /**
     * 把所有的标记从地图上清除
     * @return 无返回值
     */
    MarkerClusterer.prototype._removeMarkersFromMap = function(){
        for(var i = 0, marker; marker = this._markers[i]; i++){
            marker.isInCluster = false;
            this._map.removeOverlay(marker);
        }
    };

    /**
     * 删除单个标记
     * @param {BMap.Marker} marker 需要被删除的marker
     *
     * @return {Boolean} 删除成功返回true，否则返回false
     */
    MarkerClusterer.prototype._removeMarker = function(marker) {
        var index = indexOf(marker, this._markers);
        if (index === -1) {
            return false;
        }
        this._map.removeOverlay(marker);
        this._markers.splice(index, 1);
        return true;
    };

    /**
     * 删除单个标记
     * @param {BMap.Marker} marker 需要被删除的marker
     *
     * @return {Boolean} 删除成功返回true，否则返回false
     */
    MarkerClusterer.prototype.removeMarker = function(marker) {
        var success = this._removeMarker(marker);
        if (success) {
            this._clearLastClusters();
            this._createClusters();
        }
        return success;
    };

    /**
     * 删除一组标记
     * @param {Array<BMap.Marker>} markers 需要被删除的marker数组
     *
     * @return {Boolean} 删除成功返回true，否则返回false
     */
    MarkerClusterer.prototype.removeMarkers = function(markers) {
        var success = false;
        for (var i = 0; i < markers.length; i++) {
            var r = this._removeMarker(markers[i]);
            success = success || r;
        }

        if (success) {
            this._clearLastClusters();
            this._createClusters();
        }
        return success;
    };

    /**
     * 从地图上彻底清除所有的标记
     * @return 无返回值
     */
    MarkerClusterer.prototype.clearMarkers = function() {
        this._clearLastClusters();
        this._removeMarkersFromMap();
        this._markers = [];
    };

    /**
     * 重新生成，比如改变了属性等
     * @return 无返回值
     */
    MarkerClusterer.prototype._redraw = function () {
        this._clearLastClusters();
        this._createClusters();
    };

    /**
     * 获取网格大小
     * @return {Number} 网格大小
     */
    MarkerClusterer.prototype.getGridSize = function() {
        return this._gridSize;
    };

    /**
     * 设置网格大小
     * @param {Number} size 网格大小
     * @return 无返回值
     */
    MarkerClusterer.prototype.setGridSize = function(size) {
        this._gridSize = size;
        this._redraw();
    };

    /**
     * 获取聚合的最大缩放级别。
     * @return {Number} 聚合的最大缩放级别。
     */
    MarkerClusterer.prototype.getMaxZoom = function() {
        return this._maxZoom;
    };

    /**
     * 设置聚合的最大缩放级别
     * @param {Number} maxZoom 聚合的最大缩放级别
     * @return 无返回值
     */
    MarkerClusterer.prototype.setMaxZoom = function(maxZoom) {
        this._maxZoom = maxZoom;
        this._redraw();
    };

    /**
     * 获取聚合的样式风格集合
     * @return {Array<IconStyle>} 聚合的样式风格集合
     */
    MarkerClusterer.prototype.getStyles = function() {
        return this._styles;
    };

    /**
     * 设置聚合的样式风格集合
     * @param {Array<IconStyle>} styles 样式风格数组
     * @return 无返回值
     */
    MarkerClusterer.prototype.setStyles = function(styles) {
        this._styles = styles;
        this._redraw();
    };

    /**
     * 获取单个聚合的最小数量。
     * @return {Number} 单个聚合的最小数量。
     */
    MarkerClusterer.prototype.getMinClusterSize = function() {
        return this._minClusterSize;
    };

    /**
     * 设置单个聚合的最小数量。
     * @param {Number} size 单个聚合的最小数量。
     * @return 无返回值。
     */
    MarkerClusterer.prototype.setMinClusterSize = function(size) {
        this._minClusterSize = size;
        this._redraw();
    };

    /**
     * 获取单个聚合的落脚点是否是聚合内所有标记的平均中心。
     * @return {Boolean} true或false。
     */
    MarkerClusterer.prototype.isAverageCenter = function() {
        return this._isAverageCenter;
    };

    /**
     * 获取聚合的Map实例。
     * @return {Map} Map的示例。
     */
    MarkerClusterer.prototype.getMap = function() {
      return this._map;
    };

    /**
     * 获取所有的标记数组。
     * @return {Array<Marker>} 标记数组。
     */
    MarkerClusterer.prototype.getMarkers = function() {
        return this._markers;
    };

    /**
     * 获取聚合的总数量。
     * @return {Number} 聚合的总数量。
     */
    MarkerClusterer.prototype.getClustersCount = function() {
        var count = 0;
        for(var i = 0, cluster; cluster = this._clusters[i]; i++){
            cluster.isReal() && count++;
        }
        return count;
    };

    /**
     * @ignore
     * Cluster
     * @class 表示一个聚合对象，该聚合，包含有N个标记，这N个标记组成的范围，并有予以显示在Map上的TextIconOverlay等。
     * @constructor
     * @param {MarkerClusterer} markerClusterer 一个标记聚合器示例。
     */
    function Cluster(markerClusterer){
        this._markerClusterer = markerClusterer;
        this._map = markerClusterer.getMap();
        this._minClusterSize = markerClusterer.getMinClusterSize();
        this._isAverageCenter = markerClusterer.isAverageCenter();
        this._center = null;//落脚位置
        this._markers = [];//这个Cluster中所包含的markers
        this._gridBounds = null;//以中心点为准，向四边扩大gridSize个像素的范围，也即网格范围
        this._isReal = false; //真的是个聚合

        this._clusterMarker = new BMapLib.TextIconOverlay(this._center, this._markers.length, {"styles":this._markerClusterer.getStyles()});
        //this._map.addOverlay(this._clusterMarker);
    }

    /**
     * 向该聚合添加一个标记。
     * @param {Marker} marker 要添加的标记。
     * @return 无返回值。
     */
    Cluster.prototype.addMarker = function(marker){
        if(this.isMarkerInCluster(marker)){
            return false;
        }//也可用marker.isInCluster判断,外面判断OK，这里基本不会命中

        if (!this._center){
            this._center = marker.getPosition();
            this.updateGridBounds();//
        } else {
            if(this._isAverageCenter){
                var l = this._markers.length + 1;
                var lat = (this._center.lat * (l - 1) + marker.getPosition().lat) / l;
                var lng = (this._center.lng * (l - 1) + marker.getPosition().lng) / l;
                this._center = new BMap.Point(lng, lat);
                this.updateGridBounds();
            }//计算新的Center
        }

        marker.isInCluster = true;
        this._markers.push(marker);

        var len = this._markers.length;
        if(len < this._minClusterSize ){
            this._map.addOverlay(marker);
            //this.updateClusterMarker();
            return true;
        } else if (len === this._minClusterSize) {
            for (var i = 0; i < len; i++) {
                this._markers[i].getMap() && this._map.removeOverlay(this._markers[i]);
            }

        }
        this._map.addOverlay(this._clusterMarker);
        this._isReal = true;
        this.updateClusterMarker();
        return true;
    };

    /**
     * 判断一个标记是否在该聚合中。
     * @param {Marker} marker 要判断的标记。
     * @return {Boolean} true或false。
     */
    Cluster.prototype.isMarkerInCluster= function(marker){
        if (this._markers.indexOf) {
            return this._markers.indexOf(marker) != -1;
        } else {
            for (var i = 0, m; m = this._markers[i]; i++) {
                if (m === marker) {
                    return true;
                }
            }
        }
        return false;
    };

    /**
     * 判断一个标记是否在该聚合网格范围中。
     * @param {Marker} marker 要判断的标记。
     * @return {Boolean} true或false。
     */
    Cluster.prototype.isMarkerInClusterBounds = function(marker) {
        return this._gridBounds.containsPoint(marker.getPosition());
    };

    Cluster.prototype.isReal = function(marker) {
        return this._isReal;
    };

    /**
     * 更新该聚合的网格范围。
     * @return 无返回值。
     */
    Cluster.prototype.updateGridBounds = function() {
        var bounds = new BMap.Bounds(this._center, this._center);
        this._gridBounds = getExtendedBounds(this._map, bounds, this._markerClusterer.getGridSize());
    };

    /**
     * 更新该聚合的显示样式，也即TextIconOverlay。
     * @return 无返回值。
     */
    Cluster.prototype.updateClusterMarker = function () {
        if (this._map.getZoom() > this._markerClusterer.getMaxZoom()) {
            this._clusterMarker && this._map.removeOverlay(this._clusterMarker);
            for (var i = 0, marker; marker = this._markers[i]; i++) {
                this._map.addOverlay(marker);
            }
            return;
        }

        if (this._markers.length < this._minClusterSize) {
            this._clusterMarker.hide();
            return;
        }

        this._clusterMarker.setPosition(this._center);

        this._clusterMarker.setText(this._markers.length);

        var thatMap = this._map;
        var thatBounds = this.getBounds();
        this._clusterMarker.addEventListener("click", function(event){
            thatMap.setViewport(thatBounds);
        });

    };

    /**
     * 删除该聚合。
     * @return 无返回值。
     */
    Cluster.prototype.remove = function(){
        for (var i = 0, m; m = this._markers[i]; i++) {
                this._markers[i].getMap() && this._map.removeOverlay(this._markers[i]);
        }//清除散的标记点
        this._map.removeOverlay(this._clusterMarker);
        this._markers.length = 0;
        delete this._markers;
    }

    /**
     * 获取该聚合所包含的所有标记的最小外接矩形的范围。
     * @return {BMap.Bounds} 计算出的范围。
     */
    Cluster.prototype.getBounds = function() {
        var bounds = new BMap.Bounds(this._center,this._center);
        for (var i = 0, marker; marker = this._markers[i]; i++) {
            bounds.extend(marker.getPosition());
        }
        return bounds;
    };

    /**
     * 获取该聚合的落脚点。
     * @return {BMap.Point} 该聚合的落脚点。
     */
    Cluster.prototype.getCenter = function() {
        return this._center;
    };

})();

　　这经过测试发现_addToClosestCluster耗时最严重，进一步跟踪到这里，发现是addMarker太占资源了：

　　跟踪到 Cluster.prototype.addMarker 找到 updateClusterMarker 这个方法

　　进入 Cluster.prototype.updateClusterMarker 在下图的位置加一个return; 发现效率提供了几百倍，只是地图上再也没有热点了，因为return 屏蔽了下面的绘制。

　　仔细看了一下这个函数发现这里有个比较严重的问题，如果有5000个点，那么就会调用5000次的addMarker，也就会执行5000次的 setPosition和 setText，这样当然会慢了。应该是在 Cluster数据准备好了一次性绘制到MAP上，例如有10个聚合也只需要绘制10次而已。

于是我加一个聚合的绘制方法：

我同时屏蔽了click事件，因为发现 setViewport 会触发多次的zoomend和moveend，导致聚合被_redraw了很多次！

    Cluster.prototype.drawToMap = function(){
        this._clusterMarker.setPosition(this._center);
        this._clusterMarker.setText(this._markers.length);
        return;

        var thatMap = this._map;
        var thatBounds = this.getBounds();
        this._clusterMarker.addEventListener("click", function(event){
            thatMap.setViewport(thatBounds);    //bug! 这里多次出发 moveend  _redraw
        });
    }    

这个在 MarkerClusterer.prototype._createClusters 最后循环调用一次即可：

    MarkerClusterer.prototype._createClusters = function(){
        log('_createClusters begin..');
        var mapBounds = this._map.getBounds();
        var extendedBounds = getExtendedBounds(this._map, mapBounds, this._gridSize);
        for(var i = 0, marker; marker = this._markers[i]; i++){
            //marker 不属于任何聚合 && marker 在map视图范围内
            if(!marker.isInCluster && extendedBounds.containsPoint(marker.getPosition()) ){
                this._addToClosestCluster(marker);
            }
        }
        log('_createClusters end..');

        for(var i = 0, cluster; cluster = this._clusters[i]; i++){
            cluster.drawToMap();    //一起绘制到地图上
        }
    };

修改后有个小BUG，需要同时修改下TextIconOverlay脚本，在TextIconOverlay.prototype._updateCss里加一个判断：

    /**
    *更新相应的CSS。
    *@return 无返回值。
    */
    TextIconOverlay.prototype._updateCss = function(){
        var style = this.getStyleByText(this._text, this._styles);
        if(this._domElement){
            this._domElement.style.cssText = this._buildCssText(style);
        }
    };

经过修改后的MarkerClusterer效率提高了不少，5000个坐标下运行还是比较流畅的，到了3w个坐标还是有点吃力。

1.8w数据

1W数据

修改后的 MarkerClusterer.js

var BMapLib = window.BMapLib = BMapLib || {};
(function() {
    var getExtendedBounds = function(map, bounds, gridSize) {
            bounds = cutBoundsInRange(bounds);
            var pixelNE = map.pointToPixel(bounds.getNorthEast());
            var pixelSW = map.pointToPixel(bounds.getSouthWest());
            pixelNE.x += gridSize;
            pixelNE.y -= gridSize;
            pixelSW.x -= gridSize;
            pixelSW.y += gridSize;
            var newNE = map.pixelToPoint(pixelNE);
            var newSW = map.pixelToPoint(pixelSW);
            return new BMap.Bounds(newSW, newNE)
        };
    var cutBoundsInRange = function(bounds) {
            var maxX = getRange(bounds.getNorthEast().lng, -180, 180);
            var minX = getRange(bounds.getSouthWest().lng, -180, 180);
            var maxY = getRange(bounds.getNorthEast().lat, -74, 74);
            var minY = getRange(bounds.getSouthWest().lat, -74, 74);
            return new BMap.Bounds(new BMap.Point(minX, minY), new BMap.Point(maxX, maxY))
        };
    var getRange = function(i, mix, max) {
            mix && (i = Math.max(i, mix));
            max && (i = Math.min(i, max));
            return i
        };
    var isArray = function(source) {
            return '[object Array]' === Object.prototype.toString.call(source)
        };
    var indexOf = function(item, source) {
            var index = -1;
            if (isArray(source)) {
                if (source.indexOf) {
                    index = source.indexOf(item)
                } else {
                    for (var i = 0, m; m = source[i]; i++) {
                        if (m === item) {
                            index = i;
                            break
                        }
                    }
                }
            }
            return index
        };
    var MarkerClusterer = BMapLib.MarkerClusterer = function(map, options) {
            if (!map) {
                return
            }
            this._map = map;
            this._markers = [];
            this._clusters = [];
            var opts = options || {};
            this._gridSize = opts["gridSize"] || 60;
            this._maxZoom = opts["maxZoom"] || 18;
            this._minClusterSize = opts["minClusterSize"] || 2;
            this._isAverageCenter = false;
            if (opts['isAverageCenter'] != undefined) {
                this._isAverageCenter = opts['isAverageCenter']
            }
            this._styles = opts["styles"] || [];
            var that = this;
            this._map.addEventListener("zoomend", function() {
                that._redraw()
            });
            this._map.addEventListener("moveend", function() {
                that._redraw()
            });
            var mkrs = opts["markers"];
            isArray(mkrs) && this.addMarkers(mkrs)
        };
    MarkerClusterer.prototype.addMarkers = function(markers) {
        for (var i = 0, len = markers.length; i < len; i++) {
            this._pushMarkerTo(markers[i])
        }
        this._createClusters()
    };
    MarkerClusterer.prototype._pushMarkerTo = function(marker) {
        var index = indexOf(marker, this._markers);
        if (index === -1) {
            marker.isInCluster = false;
            this._markers.push(marker)
        }
    };
    MarkerClusterer.prototype.addMarker = function(marker) {
        this._pushMarkerTo(marker);
        this._createClusters()
    };
    MarkerClusterer.prototype._createClusters = function() {
        var mapBounds = this._map.getBounds();
        var extendedBounds = getExtendedBounds(this._map, mapBounds, this._gridSize);
        for (var i = 0, marker; marker = this._markers[i]; i++) {
            if (!marker.isInCluster && extendedBounds.containsPoint(marker.getPosition())) {
                this._addToClosestCluster(marker)
            }
        }
        for (var i = 0, cluster; cluster = this._clusters[i]; i++) {
            cluster.drawToMap()
        }
    };
    MarkerClusterer.prototype._addToClosestCluster = function(marker) {
        var distance = 4000000;
        var clusterToAddTo = null;
        var position = marker.getPosition();
        for (var i = 0, cluster; cluster = this._clusters[i]; i++) {
            var center = cluster.getCenter();
            if (center) {
                var d = this._map.getDistance(center, marker.getPosition());
                if (d < distance) {
                    distance = d;
                    clusterToAddTo = cluster
                }
            }
        }
        if (clusterToAddTo && clusterToAddTo.isMarkerInClusterBounds(marker)) {
            clusterToAddTo.addMarker(marker)
        } else {
            var cluster = new Cluster(this);
            cluster.addMarker(marker);
            this._clusters.push(cluster)
        }
    };
    MarkerClusterer.prototype._clearLastClusters = function() {
        for (var i = 0, cluster; cluster = this._clusters[i]; i++) {
            cluster.remove()
        }
        this._clusters = [];
        this._removeMarkersFromCluster()
    };
    MarkerClusterer.prototype._removeMarkersFromCluster = function() {
        for (var i = 0, marker; marker = this._markers[i]; i++) {
            marker.isInCluster = false
        }
    };
    MarkerClusterer.prototype._removeMarkersFromMap = function() {
        for (var i = 0, marker; marker = this._markers[i]; i++) {
            marker.isInCluster = false;
            this._map.removeOverlay(marker)
        }
    };
    MarkerClusterer.prototype._removeMarker = function(marker) {
        var index = indexOf(marker, this._markers);
        if (index === -1) {
            return false
        }
        this._map.removeOverlay(marker);
        this._markers.splice(index, 1);
        return true
    };
    MarkerClusterer.prototype.removeMarker = function(marker) {
        var success = this._removeMarker(marker);
        if (success) {
            this._clearLastClusters();
            this._createClusters()
        }
        return success
    };
    MarkerClusterer.prototype.removeMarkers = function(markers) {
        var success = false;
        for (var i = 0; i < markers.length; i++) {
            var r = this._removeMarker(markers[i]);
            success = success || r
        }
        if (success) {
            this._clearLastClusters();
            this._createClusters()
        }
        return success
    };
    MarkerClusterer.prototype.clearMarkers = function() {
        this._clearLastClusters();
        this._removeMarkersFromMap();
        this._markers = []
    };
    MarkerClusterer.prototype._redraw = function() {
        this._clearLastClusters();
        this._createClusters()
    };
    MarkerClusterer.prototype.getGridSize = function() {
        return this._gridSize
    };
    MarkerClusterer.prototype.setGridSize = function(size) {
        this._gridSize = size;
        this._redraw()
    };
    MarkerClusterer.prototype.getMaxZoom = function() {
        return this._maxZoom
    };
    MarkerClusterer.prototype.setMaxZoom = function(maxZoom) {
        this._maxZoom = maxZoom;
        this._redraw()
    };
    MarkerClusterer.prototype.getStyles = function() {
        return this._styles
    };
    MarkerClusterer.prototype.setStyles = function(styles) {
        this._styles = styles;
        this._redraw()
    };
    MarkerClusterer.prototype.getMinClusterSize = function() {
        return this._minClusterSize
    };
    MarkerClusterer.prototype.setMinClusterSize = function(size) {
        this._minClusterSize = size;
        this._redraw()
    };
    MarkerClusterer.prototype.isAverageCenter = function() {
        return this._isAverageCenter
    };
    MarkerClusterer.prototype.getMap = function() {
        return this._map
    };
    MarkerClusterer.prototype.getMarkers = function() {
        return this._markers
    };
    MarkerClusterer.prototype.getClustersCount = function() {
        var count = 0;
        for (var i = 0, cluster; cluster = this._clusters[i]; i++) {
            cluster.isReal() && count++
        }
        return count
    };

    function Cluster(markerClusterer) {
        this._markerClusterer = markerClusterer;
        this._map = markerClusterer.getMap();
        this._minClusterSize = markerClusterer.getMinClusterSize();
        this._isAverageCenter = markerClusterer.isAverageCenter();
        this._center = null;
        this._markers = [];
        this._gridBounds = null;
        this._isReal = false;
        this._clusterMarker = new BMapLib.TextIconOverlay(this._center, this._markers.length, {
            "styles": this._markerClusterer.getStyles()
        })
    }
    Cluster.prototype.addMarker = function(marker) {
        if (this.isMarkerInCluster(marker)) {
            return false
        }
        if (!this._center) {
            this._center = marker.getPosition();
            this.updateGridBounds()
        } else {
            if (this._isAverageCenter) {
                var l = this._markers.length + 1;
                var lat = (this._center.lat * (l - 1) + marker.getPosition().lat) / l;
                var lng = (this._center.lng * (l - 1) + marker.getPosition().lng) / l;
                this._center = new BMap.Point(lng, lat);
                this.updateGridBounds()
            }
        }
        marker.isInCluster = true;
        this._markers.push(marker);
        var len = this._markers.length;
        if (len < this._minClusterSize) {
            this._map.addOverlay(marker);
            return true
        } else if (len === this._minClusterSize) {
            for (var i = 0; i < len; i++) {
                this._markers[i].getMap() && this._map.removeOverlay(this._markers[i])
            }
        }
        this._map.addOverlay(this._clusterMarker);
        this._isReal = true;
        this.updateClusterMarker();
        return true
    };
    Cluster.prototype.isMarkerInCluster = function(marker) {
        if (this._markers.indexOf) {
            return this._markers.indexOf(marker) != -1
        } else {
            for (var i = 0, m; m = this._markers[i]; i++) {
                if (m === marker) {
                    return true
                }
            }
        }
        return false
    };
    Cluster.prototype.isMarkerInClusterBounds = function(marker) {
        return this._gridBounds.containsPoint(marker.getPosition())
    };
    Cluster.prototype.isReal = function(marker) {
        return this._isReal
    };
    Cluster.prototype.updateGridBounds = function() {
        var bounds = new BMap.Bounds(this._center, this._center);
        this._gridBounds = getExtendedBounds(this._map, bounds, this._markerClusterer.getGridSize())
    };
    Cluster.prototype.drawToMap = function() {
        this._clusterMarker.setPosition(this._center);
        this._clusterMarker.setText(this._markers.length);
        return;
        var thatMap = this._map;
        var thatBounds = this.getBounds();
        this._clusterMarker.addEventListener("click", function(event) {
            thatMap.setViewport(thatBounds)
        })
    }
    Cluster.prototype.updateClusterMarker = function() {
        if (this._map.getZoom() > this._markerClusterer.getMaxZoom()) {
            this._clusterMarker && this._map.removeOverlay(this._clusterMarker);
            for (var i = 0, marker; marker = this._markers[i]; i++) {
                this._map.addOverlay(marker)
            }
            return
        }
        if (this._markers.length < this._minClusterSize) {
            this._clusterMarker.hide();
            return
        }
        return;
        this._clusterMarker.setPosition(this._center);
        this._clusterMarker.setText(this._markers.length);
        var thatMap = this._map;
        var thatBounds = this.getBounds();
        this._clusterMarker.addEventListener("click", function(event) {
            thatMap.setViewport(thatBounds)
        })
    };
    Cluster.prototype.remove = function() {
        for (var i = 0, m; m = this._markers[i]; i++) {
            this._markers[i].getMap() && this._map.removeOverlay(this._markers[i])
        }
        this._map.removeOverlay(this._clusterMarker);
        this._markers.length = 0;
        delete this._markers
    }
    Cluster.prototype.getBounds = function() {
        var bounds = new BMap.Bounds(this._center, this._center);
        for (var i = 0, marker; marker = this._markers[i]; i++) {
            bounds.extend(marker.getPosition())
        }
        return bounds
    };
    Cluster.prototype.getCenter = function() {
        return this._center
    }
})();