Layer Opacity

<!--
  示例：图层透明度
  要点：两层瓦片叠加，setOpacity 控制上层透明度实现底图风格混合
  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>图层透明度</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:14px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar label{display:flex;gap:6px;align-items:center}
  .bar input[type=range]{width:180px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label>上层透明度 <input type="range" id="opacity" min="0" max="100" value="60">
    <b id="val">60%</b></label>
  <span>上层为 Humanitarian 样式，下层为标准 OSM</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').innerHTML =
      '<div style="padding:20px;color:#b42318">OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  var fromLonLat = ol.proj.fromLonLat;

  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'})
  });

  /* Humanitarian 样式，公益救援常用，配色与标准 OSM 差别明显 */
  var hotLayer = 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
  });

  new ol.Map({
    target: 'map',
    layers: [baseLayer, hotLayer],
    view: new ol.View({
      center: fromLonLat([116.391263, 39.907359]),
      zoom: 13
    })
  });

  document.getElementById('opacity').addEventListener('input', function () {
    var v = Number(this.value);
    hotLayer.setOpacity(v / 100);
    document.getElementById('val').textContent = v + '%';
  });
})();
</script>
</body>
</html>