Semi-Transparent Layer

Example of a map with a semi-transparent layer.

This example will display a tiled MaxBox layer semi-transparently over an OSM background. The OSM layer is changed to black and white by using a CSS filter.

main.js

import Map from 'ol/Map.js';
import OSM from 'ol/source/OSM.js';
import TileJSON from 'ol/source/TileJSON.js';
import TileLayer from 'ol/layer/Tile.js';
import View from 'ol/View.js';
import {fromLonLat} from 'ol/proj.js';

const key =
  'Your Mapbox access token from https://mapbox.com/ here';

const map = new Map({
  layers: [
    new TileLayer({
      className: 'bw',
      source: new OSM(),
    }),
    new TileLayer({
      source: new TileJSON({
        url:
          'https://api.tiles.mapbox.com/v4/mapbox.va-quake-aug.json?secure&access_token=' +
          key,
        crossOrigin: 'anonymous',
        // this layer has transparency, so do not fade tiles:
        transition: 0,
      }),
    }),
  ],
  target: 'map',
  view: new View({
    center: fromLonLat([-77.93255, 37.9555]),
    zoom: 7,
  }),
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Semi-Transparent Layer</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
      .bw {
        filter: grayscale(100%);
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>

    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "semi-transparent-layer",
  "dependencies": {
    "ol": "9.1.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}