openlayers结合turf geojson面获取面积和中心点

在 OpenLayers 中绘制 GeoJSON 面要素并计算面积和中心点，可以结合 OpenLayers 的 ol/format/GeoJSON 模块将 GeoJSON 数据转换为 OpenLayers 的 Feature，然后使用 Turf.js 进行计算。示例代码如下

import Map from 'ol/Map';
import View from 'ol/View';
import { Tile as TileLayer } from 'ol/layer';
import OSM from 'ol/source/OSM';
import { Vector as VectorLayer } from 'ol/layer';
import VectorSource from 'ol/source/Vector';
import GeoJSON from 'ol/format/GeoJSON';
import * as turf from '@turf/turf';

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

// 创建一个 GeoJSON 面要素
const geojson = {
  type: 'Feature',
  geometry: {
    type: 'Polygon',
    coordinates: [
      [
        [116.39, 39.91],
        [116.41, 39.91],
        [116.41, 39.93],
        [116.39, 39.93],
        [116.39, 39.91]
      ]
    ]
  }
};

// 将 GeoJSON 转换为 OpenLayers Feature
const vectorSource = new VectorSource({
  features: new GeoJSON().readFeatures(geojson, {
    featureProjection: 'EPSG:4326'
  })
});

const vectorLayer = new VectorLayer({ source: vectorSource });
map.addLayer(vectorLayer);

// 使用 Turf.js 计算面积和中心点
const polygon = turf.polygon(geojson.geometry.coordinates);
const area = turf.area(polygon);
const center = turf.center(polygon);

console.log('面积：', area.toFixed(2) + ' 平方米');
console.log('中心点：', center.geometry.coordinates);