Auto zoom on multipolygon with Leaflet

Question

I have a geojson with a multipolygon and I want to fit this multipolygon to the map. The map center only on one polygon not on the multipolygon.

Here is my script

    var map = L.map('map',{ zoomControl:false })
              .setView([<?php echo $lat; ?>, <?php echo $lng; ?>], 12);
    
    
            var zoomFS = new L.Control.ZoomFS(); 
    map.addControl(zoomFS);

    var defaultLayer = new L.TileLayer.MapBox.Light({minZoom: 10, maxZoom: 16});
    map.addLayer(defaultLayer);

    var info = L.control();

    info.onAdd = function (map) {
        this._div = L.DomUtil.create('div', 'info');
        this.update();
        return this._div;
    };

    info.update = function (props) {
        this._div.innerHTML = '<h4>Massifs forestiers près de </h4>' +  (props ?
            '<b>' + props.LLIB_FRT +'</b><br />'
            : 'Survolez une zone colorée');
    };

    info.addTo(map);


    // get color depending on population density value
    function getColor(d) {
        return d == 'OUI' ? '#238B45' :
               d == 'NON'  ? '#74C476' :
               '';
    }

    function style(feature) {
        return {
            weight: 1,
            opacity: 1,
            color: 'white',
            dashArray: '',
            fillOpacity: 0.7,
            fillColor: getColor(feature.properties.CDOM_FRT)
        };
    }

    function highlightFeature(e) {
        var layer = e.target;

        layer.setStyle({
            weight: 3,
            color: '#666',
            dashArray: '',
            fillOpacity: 0.7,
            fillColor: '#C7E9C0'
        });

        if (!L.Browser.ie && !L.Browser.opera) {
            layer.bringToFront();
        }

        info.update(layer.feature.properties);
    }

    var geojson;

    function resetHighlight(e) {
        geojson.resetStyle(e.target);
        info.update();
    }

    function zoomToFeature(e) {
        map.fitBounds(e.target.getBounds());
    }
    
    
    function onEachFeature(feature, layer) {
        layer.on({
            mouseover: highlightFeature,
            mouseout: resetHighlight,
            click: zoomToFeature
        });
    }

    geojson = L.geoJson(foret, {
        style: style,
        onEachFeature: onEachFeature
    }).addTo(map);
    
            map.fitBounds(map.getBounds());
    
    var legend = L.control({position: 'bottomright'});

    legend.onAdd = function (map) {

    var div = L.DomUtil.create('div', 'info legend'),
            grades = ['OUI','NON'],
            labels = [],
            from, to;

        
            labels.push(
                '<i style="background:' + getColor('OUI') + '"></i> Forêt domaniale<br />' + '<i style="background:' + getColor('NON') + '"></i> Autre forêt'
                 );
        
        
        div.innerHTML = labels.join('<br />') + '<br /><small>Source ONF</small>';
        return div;
    };


    legend.addTo(map);

And My Geojson call before the script :

var foret = {"type": "FeatureCollection","features": [{ "type": "Feature","id":"28", "properties": { "LLIB_FRT":"Forêt communale d'Hinsingen", "CDOM_FRT":"NON"}, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ 6.9943980558132, 48.946433094078 ], [ 6.994620292006, 48.946654797086 ], [ 6.9946440493621, 48.946769064939 ], [ 6.9942757111879, 48.947051596133 ], [ 6.994525224939, 48.947130121777 ], [ 6.9949682000749, 48.946963549201 ], [ 6.9953766392947, 48.947023616958 ], [ 6.9957374325074, 48.946813022271 ], [ 6.9965129612099, 48.946224218666 ], [ 6.9961325523574, 48.945968748319 ], [ 6.9957770974676, 48.945782611345 ], [ 6.9957646870665, 48.945668975401 ], [ 6.9959606190443, 48.945511036547 ], [ 6.9946195521361, 48.94466102012 ], [ 6.994630665892, 48.944546885841 ], [ 6.9947706431545, 48.944451927805 ], [ 6.9943890358713, 48.943557180488 ], [ 6.9939647083228, 48.942850378597 ], [ 6.9936098649794, 48.943031218817 ], [ 6.990978273955, 48.944169736953 ], [ 6.9907916915416, 48.944275487598 ], [ 6.9906590303195, 48.944540260439 ], [ 6.9903122282768, 48.945515871105 ], [ 6.9899779107984, 48.945891734939 ], [ 6.9897536964784, 48.946062513595 ], [ 6.9906082903887, 48.946007229028 ], [ 6.9907530326376, 48.946038714842 ], [ 6.9908245833021, 48.94612737104 ], [ 6.9909366304299, 48.946984068611 ], [ 6.9928842027716, 48.947039217107 ], [ 6.9929248400957, 48.946763159392 ], [ 6.9930024317067, 48.946669408079 ], [ 6.9931592044754, 48.946642240938 ], [ 6.9939125945186, 48.946695983544 ], [ 6.9940803721788, 48.946467213889 ], [ 6.9942616812201, 48.946401938807 ], [ 6.9943980558132, 48.946433094078 ] ],[ [ 7.0132518064932, 48.954701866676 ], [ 7.0130792746756, 48.955281720291 ], [ 7.0131097085661, 48.955406738419 ], [ 7.0134535050459, 48.956019942767 ], [ 7.0136768179147, 48.956641121897 ], [ 7.0136432241135, 48.956891471012 ], [ 7.013391660559, 48.95756050072 ], [ 7.0164377304443, 48.958126765886 ], [ 7.0173343130064, 48.958220743678 ], [ 7.0180405329659, 48.958235207654 ], [ 7.0180712371346, 48.957763530194 ], [ 7.018466890148, 48.957337559452 ], [ 7.0183245760167, 48.957321560691 ], [ 7.0182167345232, 48.957234693134 ], [ 7.0176940753708, 48.955926500229 ], [ 7.0171570061764, 48.955918750115 ], [ 7.0170252455885, 48.955885108994 ], [ 7.0165780794306, 48.955358357152 ], [ 7.016549105281, 48.955117411187 ], [ 7.0159152497559, 48.95481071823 ], [ 7.0155138192773, 48.954679378104 ], [ 7.015287839558, 48.954917146081 ], [ 7.015151253069, 48.954947663459 ], [ 7.0142533774551, 48.954711047176 ], [ 7.012862311613, 48.954409014242 ], [ 7.013130198481, 48.95455616266 ], [ 7.0132518064932, 48.954701866676 ] ] ] ] } }]};

Answer 1

Nowadays, you can use the getBounds method of a MultiPolygon object and than use that to set a map's bounds.

var multipolygon = L.geoJson(foret);
multipolygon.addTo(map);
map.fitBounds(multipolygon.getBounds());

Answer 2

I have little experience with leaflet, but this seems like a bug in getBounds when dealing with a multipolygon.

Here's a workaround to calculate the full bounds of a multipolygon:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8" />

  <meta name="viewport" content="width=device-width, initial-scale=1.0">

  <link rel="stylesheet" href="../dist/leaflet.css" />
  <!--[if lte IE 8]><link rel="stylesheet" href="../dist/leaflet.ie.css" /><![endif]-->
</head>
<body>
  <div id="map" style="width: 600px; height: 400px"></div>
  <script>
    var foret = {"type": "FeatureCollection","features": [{ "type": "Feature","id":"28", "properties": { "LLIB_FRT":"Forêt communale d'Hinsingen", "CDOM_FRT":"NON"}, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ 6.9943980558132, 48.946433094078 ], [ 6.994620292006, 48.946654797086 ], [ 6.9946440493621, 48.946769064939 ], [ 6.9942757111879, 48.947051596133 ], [ 6.994525224939, 48.947130121777 ], [ 6.9949682000749, 48.946963549201 ], [ 6.9953766392947, 48.947023616958 ], [ 6.9957374325074, 48.946813022271 ], [ 6.9965129612099, 48.946224218666 ], [ 6.9961325523574, 48.945968748319 ], [ 6.9957770974676, 48.945782611345 ], [ 6.9957646870665, 48.945668975401 ], [ 6.9959606190443, 48.945511036547 ], [ 6.9946195521361, 48.94466102012 ], [ 6.994630665892, 48.944546885841 ], [ 6.9947706431545, 48.944451927805 ], [ 6.9943890358713, 48.943557180488 ], [ 6.9939647083228, 48.942850378597 ], [ 6.9936098649794, 48.943031218817 ], [ 6.990978273955, 48.944169736953 ], [ 6.9907916915416, 48.944275487598 ], [ 6.9906590303195, 48.944540260439 ], [ 6.9903122282768, 48.945515871105 ], [ 6.9899779107984, 48.945891734939 ], [ 6.9897536964784, 48.946062513595 ], [ 6.9906082903887, 48.946007229028 ], [ 6.9907530326376, 48.946038714842 ], [ 6.9908245833021, 48.94612737104 ], [ 6.9909366304299, 48.946984068611 ], [ 6.9928842027716, 48.947039217107 ], [ 6.9929248400957, 48.946763159392 ], [ 6.9930024317067, 48.946669408079 ], [ 6.9931592044754, 48.946642240938 ], [ 6.9939125945186, 48.946695983544 ], [ 6.9940803721788, 48.946467213889 ], [ 6.9942616812201, 48.946401938807 ], [ 6.9943980558132, 48.946433094078 ] ],[ [ 7.0132518064932, 48.954701866676 ], [ 7.0130792746756, 48.955281720291 ], [ 7.0131097085661, 48.955406738419 ], [ 7.0134535050459, 48.956019942767 ], [ 7.0136768179147, 48.956641121897 ], [ 7.0136432241135, 48.956891471012 ], [ 7.013391660559, 48.95756050072 ], [ 7.0164377304443, 48.958126765886 ], [ 7.0173343130064, 48.958220743678 ], [ 7.0180405329659, 48.958235207654 ], [ 7.0180712371346, 48.957763530194 ], [ 7.018466890148, 48.957337559452 ], [ 7.0183245760167, 48.957321560691 ], [ 7.0182167345232, 48.957234693134 ], [ 7.0176940753708, 48.955926500229 ], [ 7.0171570061764, 48.955918750115 ], [ 7.0170252455885, 48.955885108994 ], [ 7.0165780794306, 48.955358357152 ], [ 7.016549105281, 48.955117411187 ], [ 7.0159152497559, 48.95481071823 ], [ 7.0155138192773, 48.954679378104 ], [ 7.015287839558, 48.954917146081 ], [ 7.015151253069, 48.954947663459 ], [ 7.0142533774551, 48.954711047176 ], [ 7.012862311613, 48.954409014242 ], [ 7.013130198481, 48.95455616266 ], [ 7.0132518064932, 48.954701866676 ] ] ] ] } }]};
  </script>
  <script src="../dist/leaflet.js"></script>

  <script>
    var map = L.map('map').setView([48.9390, 6.9797], 14);

    L.tileLayer('http://{s}.tile.cloudmade.com/{key}/22677/256/{z}/{x}/{y}.png', {
      attribution: 'Map data &copy; 2011 OpenStreetMap contributors, Imagery &copy; 2012 CloudMade',
      key: 'BC9A493B41014CAABB98F0471D759707'
    }).addTo(map);

    function onEachFeature(feature, layer) {
      if ( feature.geometry.type === "MultiPolygon" ) {
        // get the bounds for the first polygon that makes up the multipolygon
        var bounds = layer.getBounds();
        // loop through coordinates array
        // skip first element as the bounds var represents the bounds for that element
        for ( var i = 1, il = feature.geometry.coordinates[0].length; i < il; i++ ) {
          var ring = feature.geometry.coordinates[0][i];
          var latLngs = ring.map(function(pair) {
            return new L.LatLng(pair[1], pair[0]);
          });
          var nextBounds = new L.LatLngBounds(latLngs);
          bounds.extend(nextBounds);
        }
        map.fitBounds(bounds);
      }
      var popupContent = "<p>I started out as a GeoJSON " +
          feature.geometry.type + ", but now I'm a Leaflet vector!</p>";

      if (feature.properties && feature.properties.popupContent) {
        popupContent += feature.properties.popupContent;
      }

      layer.bindPopup(popupContent);
    }

    var geoJson = L.geoJson([foret], {

      style: function (feature) {
        return feature.properties && feature.properties.style;
      },
      onEachFeature: onEachFeature

    }).addTo(map);

  </script>
</body>
</html>