原文链接及内容

原文链接：https://openlayers.org/en/latest/examples/utfgrid.html

运行界面

如上图所示，将鼠标指向某个国家即可查看其名称和国旗。用TileMill制作的切片，并托管在mapbox.com上或使用开源的TileServer。

main.js代码如下：

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import Map from 'ol/Map.js';
import Overlay from 'ol/Overlay.js';
import TileJSON from 'ol/source/TileJSON.js';
import TileLayer from 'ol/layer/Tile.js';
import UTFGrid from 'ol/source/UTFGrid.js';
import View from 'ol/View.js';

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

const mapLayer = new TileLayer({
  source: new TileJSON({
    url:
      'https://api.tiles.mapbox.com/v4/mapbox.geography-class.json?secure&access_token=' +
      key,
  }),
});

const gridSource = new UTFGrid({
  url:
    'https://api.tiles.mapbox.com/v4/mapbox.geography-class.json?secure&access_token=' +
    key,
});

const gridLayer = new TileLayer({source: gridSource});

const view = new View({
  center: [0, 0],
  zoom: 1,
});

const mapElement = document.getElementById('map');
const map = new Map({
  layers: [mapLayer, gridLayer],
  target: mapElement,
  view: view,
});

const infoElement = document.getElementById('country-info');
const flagElement = document.getElementById('country-flag');
const nameElement = document.getElementById('country-name');

const infoOverlay = new Overlay({
  element: infoElement,
  offset: [15, 15],
  stopEvent: false,
});
map.addOverlay(infoOverlay);

const displayCountryInfo = function (coordinate) {
  const viewResolution = /** @type {number} */ (view.getResolution());
  gridSource.forDataAtCoordinateAndResolution(
    coordinate,
    viewResolution,
    function (data) {
      // If you want to use the template from the TileJSON,
      //  load the mustache.js library separately and call
      //  info.innerHTML = Mustache.render(gridSource.getTemplate(), data);
      mapElement.style.cursor = data ? 'pointer' : '';
      if (data) {
        flagElement.src = 'data:image/png;base64,' + data['flag_png'];
        nameElement.innerHTML = data['admin'];
      }
      infoOverlay.setPosition(data ? coordinate : undefined);
    }
  );
};

map.on('pointermove', function (evt) {
  if (evt.dragging) {
    return;
  }
  const coordinate = map.getEventCoordinate(evt.originalEvent);
  displayCountryInfo(coordinate);
});

map.on('click', function (evt) {
  displayCountryInfo(evt.coordinate);
});

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>UTFGrid</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
      #country-name {
        color: black;
        font-size: 12pt;
        font-weight: bold;
        text-shadow: white 0.1em 0.1em 0.2em;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <div style="display: none;">
      <!-- Overlay with the country info -->
      <div id="country-info">
        <div id="country-name">&nbsp;</div>
        <img id="country-flag" />
      </div>
    </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>