source: extensions/rv_gmaps/trunk/include/cluster_maker.php @ 3447

<?php

function cluster_area_compare( &$a, &$b )
{
        $aa = bounds_lat_range($a['bounds']) * bounds_lon_range($a['bounds']);
        $ab = bounds_lat_range($b['bounds']) * bounds_lon_range($b['bounds']);
        return -$aa+$ab; // biggest first
}

class ClusterMaker
{
        private $_image_map;
        private $_image_ranks;

        var $bounds;
        var $debug_str;

        function make_clusters($images, $maxLatPrecision, $maxLonPrecision, $maxNbMarkers)
        {
                $this->_image_map = $images;
                $this->_image_ranks = array();
                $this->debug_str = '';

                $start = get_moment();
                $total_iterations = 0;
                $total_generations = 0;

                $this->bounds = array();
                foreach($images as $img)
                        $this->bounds = bounds_add($this->bounds, $img['lat'], $img['lon'] );

                $pending_split = array(
                                array(
                                        'bounds' => $this->bounds,
                                        'items' => array_keys( $this->_image_map ),
                                )
                        );
                $result = array();

                while ( count($pending_split) )
                {
                        $total_generations++;
                        $next_level_to_split = array();
                        while ( count($pending_split) )
                        {
                                $current = array_shift( $pending_split );
                                $splitted = $this->_split_cluster($current, $maxLatPrecision, $maxLonPrecision );
                                if ( count($splitted)>1 )
                                {
                                        /*echo('splitted: ' . var_export($current['bounds'],true). ' in '. count($splitted)."\n" );
                                        foreach( $splitted as $k => $split )
                                                echo("sub $k: " . var_export($split['bounds'],true)."\n" );*/
                                        $total_iterations += count($current['items']);
                                        $next_level_to_split = array_merge($next_level_to_split, $splitted );
                                        if ( count($result)+count($pending_split)+count($next_level_to_split) >= $maxNbMarkers )
                                        {
                                                $result = array_merge($result, $pending_split, $next_level_to_split );
                                                $pending_split = $next_level_to_split = array();
                                                break;
                                        }
                                }
                                else
                                        array_push( $result, $current );
                        }
                        $pending_split = $next_level_to_split;
                        usort( $pending_split, 'cluster_area_compare' );
                }
                $merged = $this->_try_merge_clusters( $result, $maxLatPrecision, $maxLonPrecision );
                $this->debug_str = get_elapsed_time($start, get_moment()) .' gen:'.$total_generations.' alg:'.count($this->_image_map).'+'.$total_iterations;
                if ($merged)
                        $this->debug_str .= " merged:$merged";
                $this->_image_map = null;
                return $result;
        }

        function _try_merge_clusters(&$clusters, $maxLatPrecision, $maxLonPrecision)
        {
                $ret = 0;
                for ($i=0; $i<count($clusters)-1; $i++)
                {
                        $ci = bounds_center( $clusters[$i]['bounds'] );
                        for ($j=$i+1; $j<count($clusters); $j++)
                        {
                                $cj = bounds_center( $clusters[$j]['bounds'] );
                                if ( abs($ci['lat']-$cj['lat']) < $maxLatPrecision/2
                                        and abs($ci['lon']-$cj['lon']) < $maxLonPrecision/2 )
                                {
                                        //print_r( "i=$i; j=$j \n"); var_export( $clusters[$i]['bounds'] ); var_export( $clusters[$j]['bounds'] );
                                        $clusters[$i]['items'] = array_merge( $clusters[$i]['items'], $clusters[$j]['items'] );
                                        if ( empty($this->_image_ranks) )
                                                $this->_image_ranks = array_flip( array_keys($this->_image_map) );
                                        usort( $clusters[$i]['items'], array($this, '_image_rank_compare') );
                                        $clusters[$i]['bounds'] = bounds_union($clusters[$i]['bounds'], $clusters[$j]['bounds'] );
                                        array_splice( $clusters, $j, 1);
                                        $j--;
                                        $ci = bounds_center( $clusters[$i]['bounds'] );
                                        $ret++;
                                }
                        }
                }
                return $ret;
        }

        function _image_rank_compare($a, $b)
        {
                return $this->_image_ranks[$a] - $this->_image_ranks[$b];
        }

        function _split_cluster($cluster, $maxLatPrecision, $maxLonPrecision)
        {
                $latRange = bounds_lat_range($cluster['bounds']);
                $lonRange = bounds_lon_range($cluster['bounds']);

                $lat_nb_tiles = max( 1, $latRange/$maxLatPrecision );
                $lon_nb_tiles = max( 1, $lonRange/$maxLonPrecision );
                //echo('lat_nb '.$lat_nb_tiles.' lon_nb '.$lon_nb_tiles."\n");
                if ($lat_nb_tiles<2 and $lon_nb_tiles<2)
                        return array();

                $ll_tile_factor = $lat_nb_tiles/$lon_nb_tiles;

                if ($ll_tile_factor > 3)
                { // 1x3
                        $lat_step = $latRange/3;
                        $lon_step = $lonRange;
                }
                elseif ($ll_tile_factor < 1/3)
                { // 3x1
                        $lat_step = $latRange;
                        $lon_step = $lonRange/3;
                }
                elseif ($ll_tile_factor > 2)
                { // 2x3
                        $lat_step = max( $latRange/3, $maxLatPrecision );
                        $lon_step = max( $lonRange/2, $maxLonPrecision );
                }
                elseif ($ll_tile_factor < 1/2)
                { // 3x2
                        $lat_step = max( $latRange/2, $maxLatPrecision );
                        $lon_step = max( $lonRange/3, $maxLonPrecision );
                }
                else
                { // 3x3
                        $lat_step = max( $latRange/3, $maxLatPrecision );
                        $lon_step = max( $lonRange/3, $maxLonPrecision );
                }

                if ( $cluster['bounds']['count'] > 200 )
                {
                        if ($lat_step>4*$maxLatPrecision) $lat_step = $lat_step/2;
                        if ($lon_step>4*$maxLonPrecision) $lon_step = $lon_step/2;
                }

                $lat_step += 1e-7;
                $lon_step += 1e-7;
                //echo ( "$lat_step $latRange x $lon_step $lonRange tiles $lat_nb_tiles x $lon_nb_tiles\n" );

                $lon_nb_tiles = ceil( $lonRange / $lon_step );

                $clusters = array();
                foreach ( $cluster['items'] as $id )
                {
                        $lon = $this->_image_map[$id]['lon'];
                        $lat = $this->_image_map[$id]['lat'];

                        $idx_lon = floor ( ( $lon - $cluster['bounds']['w'] ) / $lon_step );
                        $idx_lat = floor ( ( $lat - $cluster['bounds']['s'] ) / $lat_step );

                        $idx = $lon_nb_tiles * $idx_lat + $idx_lon;

                        if ( !isset($clusters[$idx]) )
                        {
                                $clusters[$idx] = array(
                                        'bounds'  => array(),
                                        'items'   => array(),
                                        );
                        }
                        array_push( $clusters[$idx]['items'], $id );
                        $clusters[$idx]['bounds'] = bounds_add( $clusters[$idx]['bounds'] , $lat, $lon );
                }
                return $clusters;
        }
}

?>