Custom Polygon Styles

Showing the vertices of a polygon with a custom style geometry.

In this example two different styles are created for the polygons:

  • The first style is for the polygons themselves.
  • The second style is to draw the vertices of the polygons.
<!DOCTYPE html>
<html>
  <head>
    <title>Custom Polygon Styles</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v4.6.4/css/ol.css" type="text/css">
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src=""></script>
    <script src="https://openlayers.org/en/v4.6.4/build/ol.js"></script>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script>
      var styles = [
        /* We are using two different styles for the polygons:
         *  - The first style is for the polygons themselves.
         *  - The second style is to draw the vertices of the polygons.
         *    In a custom `geometry` function the vertices of a polygon are
         *    returned as `MultiPoint` geometry, which will be used to render
         *    the style.
         */
        new ol.style.Style({
          stroke: new ol.style.Stroke({
            color: 'blue',
            width: 3
          }),
          fill: new ol.style.Fill({
            color: 'rgba(0, 0, 255, 0.1)'
          })
        }),
        new ol.style.Style({
          image: new ol.style.Circle({
            radius: 5,
            fill: new ol.style.Fill({
              color: 'orange'
            })
          }),
          geometry: function(feature) {
            // return the coordinates of the first ring of the polygon
            var coordinates = feature.getGeometry().getCoordinates()[0];
            return new ol.geom.MultiPoint(coordinates);
          }
        })
      ];

      var geojsonObject = {
        'type': 'FeatureCollection',
        'crs': {
          'type': 'name',
          'properties': {
            'name': 'EPSG:3857'
          }
        },
        'features': [{
          'type': 'Feature',
          'geometry': {
            'type': 'Polygon',
            'coordinates': [[[-5e6, 6e6], [-5e6, 8e6], [-3e6, 8e6],
              [-3e6, 6e6], [-5e6, 6e6]]]
          }
        }, {
          'type': 'Feature',
          'geometry': {
            'type': 'Polygon',
            'coordinates': [[[-2e6, 6e6], [-2e6, 8e6], [0, 8e6],
              [0, 6e6], [-2e6, 6e6]]]
          }
        }, {
          'type': 'Feature',
          'geometry': {
            'type': 'Polygon',
            'coordinates': [[[1e6, 6e6], [1e6, 8e6], [3e6, 8e6],
              [3e6, 6e6], [1e6, 6e6]]]
          }
        }, {
          'type': 'Feature',
          'geometry': {
            'type': 'Polygon',
            'coordinates': [[[-2e6, -1e6], [-1e6, 1e6],
              [0, -1e6], [-2e6, -1e6]]]
          }
        }]
      };

      var source = new ol.source.Vector({
        features: (new ol.format.GeoJSON()).readFeatures(geojsonObject)
      });

      var layer = new ol.layer.Vector({
        source: source,
        style: styles
      });

      var map = new ol.Map({
        layers: [layer],
        target: 'map',
        view: new ol.View({
          center: [0, 3000000],
          zoom: 2
        })
      });
    </script>
  </body>
</html>