原文链接及内容

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

运行界面

这个例子使用layer.setextent()方法来限制覆盖图层的范围。使用上面的控件可以根据范围(近似国家边界)限制渲染。

main.js代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
import Map from 'ol/Map.js';
import TileJSON from 'ol/source/TileJSON.js';
import TileLayer from 'ol/layer/Tile.js';
import View from 'ol/View.js';
import {transformExtent} from 'ol/proj.js';

function transform(extent) {
  return transformExtent(extent, 'EPSG:4326', 'EPSG:3857');
}

const extents = {
  India: transform([68.17665, 7.96553, 97.40256, 35.49401]),
  Argentina: transform([-73.41544, -55.25, -53.62835, -21.83231]),
  Nigeria: transform([2.6917, 4.24059, 14.57718, 13.86592]),
  Sweden: transform([11.02737, 55.36174, 23.90338, 69.10625]),
};

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

const base = new TileLayer({
  source: new TileJSON({
    url:
      'https://api.tiles.mapbox.com/v4/mapbox.world-light.json?secure&access_token=' +
      key,
    crossOrigin: 'anonymous',
  }),
});

const overlay = new TileLayer({
  extent: extents.India,
  source: new TileJSON({
    url:
      'https://api.tiles.mapbox.com/v4/mapbox.world-black.json?secure&access_token=' +
      key,
    crossOrigin: 'anonymous',
  }),
});

const map = new Map({
  layers: [base, overlay],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 1,
  }),
});

for (const key in extents) {
  document.getElementById(key).onclick = function (event) {
    overlay.setExtent(extents[event.target.id]);
  };
}

界面布局文件index.html代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Limited Layer Extent</title>
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/css/bootstrap.min.css">
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <button type="button" class="btn btn-light" id="India">India</button>
    <button type="button" class="btn btn-light" id="Argentina">Argentina</button>
    <button type="button" class="btn btn-light" id="Nigeria">Nigeria</button>
    <button type="button" class="btn btn-light" id="Sweden">Sweden</button>
    <!-- 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>