Scale Line

<!--
  示例：比例尺
  要点：ol.control.ScaleLine 条形比例尺，moveend 时换算分辨率与比例分母
  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>比例尺</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:18px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar b{color:#16181d;font-family:ui-monospace,Consolas,monospace;font-weight:500}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
  .ol-scale-bar{left:12px;bottom:12px}
</style>
</head>
<body>
<div class="bar">
  <span>分辨率 <b id="res">—</b> 米/像素</span>
  <span>比例 <b id="scale">—</b></span>
  <span>级别 <b id="zoom">—</b></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 scaleLine = new ol.control.ScaleLine({
    units: 'metric',
    bar: true,
    steps: 4,
    text: true,
    minWidth: 120
  });

  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'}) })
    ],
    view: new ol.View({
      center: ol.proj.fromLonLat([116.391263, 39.907359]),
      zoom: 12
    }),
    controls: ol.control.defaults.defaults({
      attribution: false,
      rotate: false
    }).extend([scaleLine])
  });

  var resEl = document.getElementById('res');
  var scaleEl = document.getElementById('scale');
  var zoomEl = document.getElementById('zoom');

  function refresh() {
    var view = map.getView();
    var resolution = view.getResolution();

    resEl.textContent = resolution.toFixed(2);
    /* 1 米 = 39.37 英寸，按 96 dpi 换算平面比例尺 */
    scaleEl.textContent = '1 : ' + Math.round(resolution * 39.37 * 96).toLocaleString('zh-CN');
    zoomEl.textContent = view.getZoom().toFixed(2);
  }

  map.on('moveend', refresh);
  refresh();
})();
</script>
</body>
</html>