Topojson

<!--
  示例：OpenLayers TopoJSON 数据
  要点：页面内 TopoJSON 拓扑对象经 ol.format.TopoJSON 解析为矢量要素
  依赖：OpenLayers 10.3.1 · jsDelivr CDN
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>TopoJSON 数据</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@10.3.1/ol.css">
<style>
  html,body{height:100%;margin:0}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:10px;align-items:center;flex-wrap:wrap;font-size:12px;color:#58606e}
  .bar label{display:flex;gap:5px;align-items:center;cursor:pointer}
  .bar select,.bar input[type=range]{font-size:12px}
  .bar .val{font-family:ui-monospace,Consolas,monospace;color:#1f5fd0;min-width:44px}
  .bar .sep{width:1px;height:16px;background:#d8dce2}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <span>TopoJSON 对象：3 个区域 / 3 条弧段</span>
  <span class="sep"></span>
  <span id="info">—</span>
</div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/ol@10.3.1/dist/ol.js"></script>
<script>
(function () {
  'use strict';

  if (typeof ol === 'undefined') {
    document.getElementById('map').textContent = 'OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net';
    return;
  }


  var topo = {
    type: 'Topology',
    objects: {
      regions: {
        type: 'GeometryCollection',
        geometries: [
          {type: 'Polygon', arcs: [[0]], properties: {name: '北部片区', code: 'A'}},
          {type: 'Polygon', arcs: [[1]], properties: {name: '东北片区', code: 'B'}},
          {type: 'Polygon', arcs: [[2]], properties: {name: '南部片区', code: 'C'}}
        ]
      }
    },
    arcs: [
      [[116.10, 39.80], [116.30, 39.80], [116.30, 40.00], [116.10, 40.00], [116.10, 39.80]],
      [[116.30, 39.80], [116.50, 39.80], [116.50, 40.00], [116.30, 40.00], [116.30, 39.80]],
      [[116.10, 39.55], [116.50, 39.55], [116.50, 39.80], [116.10, 39.80], [116.10, 39.55]]
    ]
  };

  var features = new ol.format.TopoJSON().readFeatures(topo, {
    dataProjection: 'EPSG:4326',
    featureProjection: 'EPSG:3857'
  });

  var colors = ['#a9c9ec', '#b7dbb2', '#efcf9f'];

  var vector = new ol.layer.Vector({
    source: new ol.source.Vector({features: features}),
    style: function (feature) {
      var index = feature.get('code').charCodeAt(0) - 65;
      return new ol.style.Style({
        fill: new ol.style.Fill({color: colors[index % colors.length]}),
        stroke: new ol.style.Stroke({color: '#4f6070', width: 1}),
        text: new ol.style.Text({
          text: feature.get('name'),
          font: '500 12px sans-serif',
          fill: new ol.style.Fill({color: '#1f2b36'}),
          stroke: new ol.style.Stroke({color: '#ffffff', width: 3})
        })
      });
    }
  });

  var map = new ol.Map({
    target: 'map',
    layers: [
      new ol.layer.Tile({source: new ol.source.XYZ({url: 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}', attributions: 'Tiles © Esri'}), opacity: 0.6}),
      vector
    ],
    view: new ol.View({
      center: ol.proj.fromLonLat([116.30, 39.80]),
      zoom: 10
    })
  });

  map.on('pointermove', function (evt) {
    if (evt.dragging) {
      return;
    }
    var feature = map.forEachFeatureAtPixel(evt.pixel, function (candidate) {
      return candidate;
    });
    document.getElementById('info').textContent = feature
      ? feature.get('name') + ' · 弧段 ' + (feature.get('code') === 'A' ? '0' : feature.get('code') === 'B' ? '1' : '2')
      : '—';
  });

})();
</script>
</body>
</html>