Style Renderer

<!--
  示例：自定义样式渲染器
  要点：Style 的 renderer 回调拿到坐标数组与画布，可画任意自定义图形
  依赖：OpenLayers 10.3.1 · jsDelivr CDN（底图 OSM，无 Key）
-->
<!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>自定义样式渲染器</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;color:#16181d}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:14px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar b{color:#16181d;font-weight:600}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <span>扇形指针表示负荷占比，外圈弧线为容量</span>
  <span>悬停改数值：<b id="val">0.65</b></span>
  <input type="range" id="r" min="10" max="95" value="65" style="width:140px">
</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 (!window.ol) {
    document.getElementById('map').textContent = 'OpenLayers 加载失败，请检查 cdn.jsdelivr.net 是否可访问';
    return;
  }

  var ratio = 0.65;

  /* renderer 收到的 coordinates 是当前要素几何在屏幕上的像素坐标数组 */
  function gaugeRenderer(coordinates, state) {
    var ctx = state.context;
    var cx = coordinates[0][0];
    var cy = coordinates[0][1];
    var r = 14;

    ctx.save();
    ctx.beginPath();
    ctx.arc(cx, cy, r, 0, Math.PI * 2);
    ctx.fillStyle = 'rgba(31,95,208,.14)';
    ctx.fill();
    ctx.lineWidth = 3;
    ctx.strokeStyle = '#1f5fd0';
    ctx.stroke();

    ctx.beginPath();
    ctx.moveTo(cx, cy);
    ctx.arc(cx, cy, r - 4, -Math.PI / 2, -Math.PI / 2 + ratio * Math.PI * 2);
    ctx.closePath();
    ctx.fillStyle = ratio > 0.85 ? '#b42318' : (ratio > 0.6 ? '#d9822b' : '#2f8f5b');
    ctx.fill();
    ctx.restore();
  }

  var POINTS = [
    ['变电站 A', 116.352, 39.930],
    ['变电站 B', 116.420, 39.945],
    ['变电站 C', 116.455, 39.895],
    ['变电站 D', 116.380, 39.870]
  ];

  var feats = POINTS.map(function (p) {
    return new ol.Feature({
      geometry: new ol.geom.Point(ol.proj.fromLonLat([p[1], p[2]])),
      name: p[0]
    });
  });

  var layer = new ol.layer.Vector({
    source: new ol.source.Vector({ features: feats }),
    style: function (f) {
      return new ol.style.Style({
        renderer: gaugeRenderer,
        text: new ol.style.Text({
          text: f.get('name'),
          offsetY: 26,
          textAlign: 'center',
          font: '500 11px sans-serif',
          fill: new ol.style.Fill({ color: '#16181d' }),
          stroke: new ol.style.Stroke({ color: '#fff', 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'}) }), layer],
    view: new ol.View({ center: ol.proj.fromLonLat([116.40, 39.91]), zoom: 13 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  document.getElementById('r').addEventListener('input', function () {
    ratio = Number(this.value) / 100;
    document.getElementById('val').textContent = ratio.toFixed(2);
    layer.changed();
  });
})();
</script>
</body>
</html>