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WebGL Vector Layer

发布于 2022-11-30 23:36:07 字数 3358 浏览 0 评论 0 收藏 0

Example of a vector layer rendered using WebGL

The ecoregions are loaded from a GeoJSON file.

main.js

import GeoJSON from 'ol/format/GeoJSON';
import Layer from 'ol/layer/Layer';
import Map from 'ol/Map';
import OSM from 'ol/source/OSM';
import TileLayer from 'ol/layer/WebGLTile';
import VectorSource from 'ol/source/Vector';
import View from 'ol/View';
import WebGLVectorLayerRenderer from 'ol/renderer/webgl/VectorLayer';
import {asArray} from 'ol/color';
import {packColor} from 'ol/renderer/webgl/shaders';

class WebGLLayer extends Layer {
  createRenderer() {
    return new WebGLVectorLayerRenderer(this, {
      fill: {
        attributes: {
          color: function (feature) {
            const color = asArray(feature.get('COLOR') || '#eee');
            color[3] = 0.85;
            return packColor(color);
          },
          opacity: function () {
            return 0.6;
          },
        },
      },
      stroke: {
        attributes: {
          color: function (feature) {
            const color = [...asArray(feature.get('COLOR') || '#eee')];
            color.forEach((_, i) => (color[i] = Math.round(color[i] * 0.75))); // darken slightly
            return packColor(color);
          },
          width: function () {
            return 1.5;
          },
          opacity: function () {
            return 1;
          },
        },
      },
    });
  }
}

const osm = new TileLayer({
  source: new OSM(),
});

const vectorLayer = new WebGLLayer({
  source: new VectorSource({
    url: 'https://openlayers.org/data/vector/ecoregions.json',
    format: new GeoJSON(),
  }),
});

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

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>WebGL Vector Layer</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "webgl-vector-layer",
  "dependencies": {
    "ol": "7.0.0"
  },
  "devDependencies": {
    "vite": "^3.0.3",
    "@babel/core": "latest"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}

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