Drag Zoom

<!--
  示例：矩形缩放
  要点：DragZoom 绑定 altKeyOnly，duration 控制缩放动画，读取视图层级与分辨率
  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>矩形缩放</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;font-size:12px;color:#58606e}
  .bar button{padding:4px 10px;border:1px solid #cfd4dc;border-radius:4px;
              background:#fff;cursor:pointer;font-size:12px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <span>按住 Alt 拖拽拉框</span>
  <span id="info">—</span>
  <button id="reset">恢复初始视图</button>
</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 HOME = ol.proj.fromLonLat([116.3974, 39.9093]);

  var view = new ol.View({
    center: HOME,
    zoom: 12,
    minZoom: 3,
    maxZoom: 18
  });

  var dragZoom = new ol.interaction.DragZoom({
    condition: ol.events.condition.altKeyOnly,
    duration: 300
  });

  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: view,
    interactions: ol.interaction.defaults.defaults({
      shiftDragZoom: false
    }).extend([dragZoom]),
    controls: ol.control.defaults.defaults({ attribution: false })
  });

  var info = document.getElementById('info');

  function report() {
    info.textContent = 'zoom ' + view.getZoom().toFixed(2) +
      ' · 分辨率 ' + view.getResolution().toFixed(2) + ' m/px';
  }

  view.on('change:resolution', report);
  report();

  document.getElementById('reset').addEventListener('click', function () {
    view.animate({ center: HOME, zoom: 12, duration: 400 });
  });
})();
</script>
</body>
</html>