GeoJSON要素【译】

原文链接及内容

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

GeoJSON要素示例。

main.js代码如下：

import Circle from 'ol/geom/Circle.js';
import Feature from 'ol/Feature.js';
import GeoJSON from 'ol/format/GeoJSON.js';
import Map from 'ol/Map.js';
import View from 'ol/View.js';
import {Circle as CircleStyle, Fill, Stroke, Style} from 'ol/style.js';
import {OSM, Vector as VectorSource} from 'ol/source.js';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';

const image = new CircleStyle({
  radius: 5,
  fill: null,
  stroke: new Stroke({color: 'red', width: 1}),
});

const styles = {
  'Point': new Style({
    image: image,
  }),
  'LineString': new Style({
    stroke: new Stroke({
      color: 'green',
      width: 1,
    }),
  }),
  'MultiLineString': new Style({
    stroke: new Stroke({
      color: 'green',
      width: 1,
    }),
  }),
  'MultiPoint': new Style({
    image: image,
  }),
  'MultiPolygon': new Style({
    stroke: new Stroke({
      color: 'yellow',
      width: 1,
    }),
    fill: new Fill({
      color: 'rgba(255, 255, 0, 0.1)',
    }),
  }),
  'Polygon': new Style({
    stroke: new Stroke({
      color: 'blue',
      lineDash: [4],
      width: 3,
    }),
    fill: new Fill({
      color: 'rgba(0, 0, 255, 0.1)',
    }),
  }),
  'GeometryCollection': new Style({
    stroke: new Stroke({
      color: 'magenta',
      width: 2,
    }),
    fill: new Fill({
      color: 'magenta',
    }),
    image: new CircleStyle({
      radius: 10,
      fill: null,
      stroke: new Stroke({
        color: 'magenta',
      }),
    }),
  }),
  'Circle': new Style({
    stroke: new Stroke({
      color: 'red',
      width: 2,
    }),
    fill: new Fill({
      color: 'rgba(255,0,0,0.2)',
    }),
  }),
};

const styleFunction = function (feature) {
  return styles[feature.getGeometry().getType()];
};

const geojsonObject = {
  'type': 'FeatureCollection',
  'crs': {
    'type': 'name',
    'properties': {
      'name': 'EPSG:3857',
    },
  },
  'features': [
    {
      'type': 'Feature',
      'geometry': {
        'type': 'Point',
        'coordinates': [0, 0],
      },
    },
    {
      'type': 'Feature',
      'geometry': {
        'type': 'LineString',
        'coordinates': [
          [4e6, -2e6],
          [8e6, 2e6],
        ],
      },
    },
    {
      'type': 'Feature',
      'geometry': {
        'type': 'LineString',
        'coordinates': [
          [4e6, 2e6],
          [8e6, -2e6],
        ],
      },
    },
    {
      'type': 'Feature',
      'geometry': {
        'type': 'Polygon',
        'coordinates': [
          [
            [-5e6, -1e6],
            [-3e6, -1e6],
            [-4e6, 1e6],
            [-5e6, -1e6],
          ],
        ],
      },
    },
    {
      'type': 'Feature',
      'geometry': {
        'type': 'MultiLineString',
        'coordinates': [
          [
            [-1e6, -7.5e5],
            [-1e6, 7.5e5],
          ],
          [
            [1e6, -7.5e5],
            [1e6, 7.5e5],
          ],
          [
            [-7.5e5, -1e6],
            [7.5e5, -1e6],
          ],
          [
            [-7.5e5, 1e6],
            [7.5e5, 1e6],
          ],
        ],
      },
    },
    {
      'type': 'Feature',
      'geometry': {
        'type': 'MultiPolygon',
        'coordinates': [
          [
            [
              [-5e6, 6e6],
              [-3e6, 6e6],
              [-3e6, 8e6],
              [-5e6, 8e6],
              [-5e6, 6e6],
            ],
          ],
          [
            [
              [-2e6, 6e6],
              [0, 6e6],
              [0, 8e6],
              [-2e6, 8e6],
              [-2e6, 6e6],
            ],
          ],
          [
            [
              [1e6, 6e6],
              [3e6, 6e6],
              [3e6, 8e6],
              [1e6, 8e6],
              [1e6, 6e6],
            ],
          ],
        ],
      },
    },
    {
      'type': 'Feature',
      'geometry': {
        'type': 'GeometryCollection',
        'geometries': [
          {
            'type': 'LineString',
            'coordinates': [
              [-5e6, -5e6],
              [0, -5e6],
            ],
          },
          {
            'type': 'Point',
            'coordinates': [4e6, -5e6],
          },
          {
            'type': 'Polygon',
            'coordinates': [
              [
                [1e6, -6e6],
                [3e6, -6e6],
                [2e6, -4e6],
                [1e6, -6e6],
              ],
            ],
          },
        ],
      },
    },
  ],
};

const vectorSource = new VectorSource({
  features: new GeoJSON().readFeatures(geojsonObject),
});

vectorSource.addFeature(new Feature(new Circle([5e6, 7e6], 1e6)));

const vectorLayer = new VectorLayer({
  source: vectorSource,
  style: styleFunction,
});

const map = new Map({
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
    vectorLayer,
  ],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2,
  }),
});

界面布局文件index.html代码如下：

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>GeoJSON</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://cdn.jsdelivr.net/npm/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>