Vector Clipping Layer

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Vector Clipping Layer

Vector Clipping Layer example

Example of a clipping layer based on a vector source

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index.html<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Vector Clipping Layer</title>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
      #map {
        background: transparent;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="index.js"></script>
  </body>
</html>

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index.jsimport 'ol/ol.css';
import Map from 'ol/Map';
import View from 'ol/View';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
import VectorSource from 'ol/source/Vector';
import GeoJSON from 'ol/format/GeoJSON';
import OSM from 'ol/source/OSM';
import {Fill, Style} from 'ol/style';
import {getVectorContext} from 'ol/render';
import {fromLonLat} from 'ol/proj';

var base = new TileLayer({
  source: new OSM()
});

var clipLayer = new VectorLayer({
  style: null,
  source: new VectorSource({
    url:
    './data/geojson/switzerland.geojson',
    format: new GeoJSON()
  })
});

var style = new Style({
  fill: new Fill({
    color: 'black'
  })
});

base.on('postrender', function(e) {
  e.context.globalCompositeOperation = 'destination-in';
  var vectorContext = getVectorContext(e);
  clipLayer.getSource().forEachFeature(function(feature) {
    vectorContext.drawFeature(feature, style);
  });
  e.context.globalCompositeOperation = 'source-over';
});

var map = new Map({
  layers: [base, clipLayer],
  target: 'map',
  view: new View({
    center: fromLonLat([8.23, 46.86]),
    zoom: 7
  })
});

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package.json{
  "name": "layer-clipping-vector",
  "dependencies": {
    "ol": "6.3.1"
  },
  "devDependencies": {
    "parcel": "1.11.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --experimental-scope-hoisting --public-url . index.html"
  }
}