原文链接及内容

原文链接：https://openlayers.org/en/latest/examples/semi-transparent-layer.html

运行界面

这个例子将在OSM底图上渲染一个半透明的MaxBox平铺图层，使用CSS滤镜(CSS filter)将OSM图层更改为黑色和白色。

main.js代码如下：

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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,
  }),
});

界面布局文件index.html代码如下：

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<!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>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://cdn.jsdelivr.net/npm/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>