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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.

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index.html<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Semi-Transparent 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=requestAnimationFrame,Element.prototype.classList,URL"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
      .bw {
        filter: grayscale(100%);
      }
    </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 TileLayer from 'ol/layer/Tile';
import {fromLonLat} from 'ol/proj';
import OSM from 'ol/source/OSM';
import TileJSON from 'ol/source/TileJSON';

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

var 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
  })
});
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package.json{
  "name": "semi-transparent-layer",
  "dependencies": {
    "ol": "6.1.1"
  },
  "devDependencies": {
    "parcel": "1.11.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --experimental-scope-hoisting --public-url . index.html"
  }
}