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限制图层范围

发布于 2022-11-30 23:36:04 字数 3864 浏览 0 评论 0 收藏 0

在有限的范围内限制图层的渲染。

这个例子使用layer.setExtent()方法来修改覆盖层的范围。使用上面的控件，根据一个范围（近似的国家范围）来限制渲染。本示例演示使用 layer.setExtent() 方法来修改覆盖图层的范围。使用上边的控件，依据一个范围来限制渲染（国家近似边界）。

main.js

import 'ol/ol.css';
import Map from 'ol/Map';
import TileJSON from 'ol/source/TileJSON';
import TileLayer from 'ol/layer/Tile';
import View from 'ol/View';
import {transformExtent} from 'ol/proj';

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]);
  };
}

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Limited Layer Extent</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="./resources/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL,TextDecoder,Number.isInteger"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <button type="button" class="btn btn-default" id="India">India</button>
    <button type="button" class="btn btn-default" id="Argentina">Argentina</button>
    <button type="button" class="btn btn-default" id="Nigeria">Nigeria</button>
    <button type="button" class="btn btn-default" id="Sweden">Sweden</button>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "layer-extent",
  "dependencies": {
    "ol": "7.1.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}

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