Layer Opacity

Layer opacity

Adjust layer opacity based on user input

The layer.setOpacity() method can be called to adjust the opacity of a layer.

main.js

import 'ol/ol.css';
import Map from 'ol/Map';
import OSM from 'ol/source/OSM';
import TileLayer from 'ol/layer/WebGLTile';
import View from 'ol/View';
import XYZ from 'ol/source/XYZ';

const key = 'Get your own API key at https://www.maptiler.com/cloud/';

const imagery = new TileLayer({
  className: 'ol-layer-imagery',
  source: new XYZ({
    attributions:
      '<a href="https://www.maptiler.com/copyright/" target="_blank">&copy; MapTiler</a> ',
    url: 'https://api.maptiler.com/tiles/satellite/{z}/{x}/{y}.jpg?key=' + key,
    maxZoom: 20,
    crossOrigin: '',
  }),
});

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

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

const opacityInput = document.getElementById('opacity-input');
const opacityOutput = document.getElementById('opacity-output');
function update() {
  const opacity = parseFloat(opacityInput.value);
  osm.setOpacity(opacity);
  opacityOutput.innerText = opacity.toFixed(2);
}
opacityInput.addEventListener('input', update);
opacityInput.addEventListener('change', update);
update();

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Layer Opacity</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></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>
    <label>
      Layer opacity
      <input id="opacity-input" type="range" min="0" max="1" step="0.01" value="1" />
      <span id="opacity-output"></span>
    </label>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "layer-opacity",
  "dependencies": {
    "ol": "6.12.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}