Semi Transparent Layer

<!--
  示例：半透明图层
  要点：layer.setOpacity 只影响该层，叠加层与底图互不干扰
  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>半透明图层</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:18px;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>专题层不透明度 <b id="v1">60</b>%</span>
  <input type="range" id="r1" min="0" max="100" value="60" style="width:150px">
  <span>底图不透明度 <b id="v2">100</b>%</span>
  <input type="range" id="r2" min="0" max="100" value="100" style="width:150px">
</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 ZONES = [
    ['核心区', 116.38, 39.91, 0.06],
    ['拓展区', 116.47, 39.95, 0.05],
    ['生态区', 116.28, 39.97, 0.04]
  ];

  var feats = ZONES.map(function (z) {
    return new ol.Feature({
      geometry: new ol.geom.Circle(ol.proj.fromLonLat([z[1], z[2]]), z[3] * 111000),
      name: z[0]
    });
  });

  var overlayLayer = new ol.layer.Vector({
    source: new ol.source.Vector({ features: feats }),
    opacity: 0.6
  });
  overlayLayer.setStyle(function (f) {
    return new ol.style.Style({
      fill: new ol.style.Fill({ color: '#d64545' }),
      stroke: new ol.style.Stroke({ color: '#8f1f1f', width: 2 }),
      text: new ol.style.Text({
        text: f.get('name'),
        font: '600 13px sans-serif',
        fill: new ol.style.Fill({ color: '#ffffff' })
      })
    });
  });

  var baseLayer = 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'}) });

  var map = new ol.Map({
    target: 'map',
    layers: [baseLayer, overlayLayer],
    view: new ol.View({ center: ol.proj.fromLonLat([116.40, 39.94]), zoom: 11 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  document.getElementById('r1').addEventListener('input', function () {
    document.getElementById('v1').textContent = this.value;
    overlayLayer.setOpacity(this.value / 100);
  });

  document.getElementById('r2').addEventListener('input', function () {
    document.getElementById('v2').textContent = this.value;
    baseLayer.setOpacity(this.value / 100);
  });
})();
</script>
</body>
</html>