Clustered Features

Example of using ol/source/Cluster.

This example shows how to do clustering on point features.

main.js

import 'ol/ol.css';
import Feature from 'ol/Feature';
import Map from 'ol/Map';
import Point from 'ol/geom/Point';
import View from 'ol/View';
import {
  Circle as CircleStyle,
  Fill,
  Stroke,
  Style,
  Text,
} from 'ol/style';
import {Cluster, OSM, Vector as VectorSource} from 'ol/source';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
import {boundingExtent} from 'ol/extent';

const distanceInput = document.getElementById('distance');
const minDistanceInput = document.getElementById('min-distance');

const count = 20000;
const features = new Array(count);
const e = 4500000;
for (let i = 0; i < count; ++i) {
  const coordinates = [2 * e * Math.random() - e, 2 * e * Math.random() - e];
  features[i] = new Feature(new Point(coordinates));
}

const source = new VectorSource({
  features: features,
});

const clusterSource = new Cluster({
  distance: parseInt(distanceInput.value, 10),
  minDistance: parseInt(minDistanceInput.value, 10),
  source: source,
});

const styleCache = {};
const clusters = new VectorLayer({
  source: clusterSource,
  style: function (feature) {
    const size = feature.get('features').length;
    let style = styleCache[size];
    if (!style) {
      style = new Style({
        image: new CircleStyle({
          radius: 10,
          stroke: new Stroke({
            color: '#fff',
          }),
          fill: new Fill({
            color: '#3399CC',
          }),
        }),
        text: new Text({
          text: size.toString(),
          fill: new Fill({
            color: '#fff',
          }),
        }),
      });
      styleCache[size] = style;
    }
    return style;
  },
});

const raster = new TileLayer({
  source: new OSM(),
});

const map = new Map({
  layers: [raster, clusters],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2,
  }),
});

const distanceHandler = function () {
  clusterSource.setDistance(parseInt(distanceInput.value, 10));
};
distanceInput.addEventListener('input', distanceHandler);
distanceInput.addEventListener('change', distanceHandler);

const minDistanceHandler = function () {
  clusterSource.setMinDistance(parseInt(minDistanceInput.value, 10));
};
minDistanceInput.addEventListener('input', minDistanceHandler);
minDistanceInput.addEventListener('change', minDistanceHandler);

map.on('click', (e) => {
  clusters.getFeatures(e.pixel).then((clickedFeatures) => {
    if (clickedFeatures.length) {
      // Get clustered Coordinates
      const features = clickedFeatures[0].get('features');
      if (features.length > 1) {
        const extent = boundingExtent(
          features.map((r) => r.getGeometry().getCoordinates())
        );
        map.getView().fit(extent, {duration: 1000, padding: [50, 50, 50, 50]});
      }
    }
  });
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Clustered Features</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <!-- The lines below are only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,TextDecoder"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/core-js/3.18.3/minified.js"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <form>
      <div class="form-group">
        <label for="distance" class="col-form-label">Cluster distance</label>
        <input id="distance" class="form-control-range" type="range" min="0" max="200" step="1" value="40"/>
        <small class="form-text text-muted">
          The distance within which features will be clustered together.
        </small>
      </div>
      <div class="form-group">
        <label for="min-distance" class="col-form-label">Minimum distance</label>
        <input id="min-distance" class="form-control-range" type="range" min="0" max="200" step="1" value="20"/>
        <small class="form-text text-muted">
          The minimum distance between clusters. Can't be larger than the configured distance.
        </small>
      </div>
    </form>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "cluster",
  "dependencies": {
    "ol": "6.13.1-dev"
  },
  "devDependencies": {
    "parcel": "^2.0.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}