Export Pdf

<!--
  示例：地图导出为 PDF — OpenLayers export-pdf
  核心逻辑：rendercomplete 后合成各图层 canvas，加标题条，再交给浏览器打印成 PDF
  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>地图导出为 PDF</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;flex-wrap:wrap}
  .bar button{font:inherit;padding:3px 9px;border:1px solid #ccd2da;background:#fff;
       border-radius:3px;cursor:pointer;color:#2b3140}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <button id="export">导出 A4 版式</button>
  <span id="info">导出后在新窗口按 Ctrl+P 选择「另存为 PDF」</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 infoEl = document.getElementById('info');

  var points = [
    [116.391263, 39.907359, '天安门'],
    [116.410600, 39.914700, '王府井'],
    [116.374200, 39.909700, '西单'],
    [116.438400, 39.916900, '东单']
  ].map(function (p) {
    return new ol.Feature({
      geometry: new ol.geom.Point(ol.proj.fromLonLat([p[0], p[1]])),
      name: p[2]
    });
  });

  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'}) }),
      new ol.layer.Vector({
        source: new ol.source.Vector({ features: points }),
        style: function (feature) {
          return new ol.style.Style({
            image: new ol.style.Circle({
              radius: 5,
              fill: new ol.style.Fill({ color: '#1f5fd0' }),
              stroke: new ol.style.Stroke({ color: '#fff', width: 2 })
            }),
            text: new ol.style.Text({
              text: feature.get('name'),
              offsetY: -13,
              font: '500 12px sans-serif',
              fill: new ol.style.Fill({ color: '#16181d' }),
              stroke: new ol.style.Stroke({ color: '#fff', width: 3 })
            })
          });
        }
      })
    ],
    view: new ol.View({
      center: ol.proj.fromLonLat([116.391, 39.907]),
      zoom: 13,
      minZoom: 2
    }),
    controls: ol.control.defaults.defaults({ attribution: false })
  });

  /* A4 横向 96dpi 约 1123 × 794 像素 */
  var PAGE_W = 1123;
  var PAGE_H = 794;
  var TITLE_H = 72;

  document.getElementById('export').addEventListener('click', function () {
    infoEl.textContent = '正在合成图层…';

    map.once('rendercomplete', function () {
      var mapSize = map.getSize();
      var canvas = document.createElement('canvas');
      canvas.width = PAGE_W;
      canvas.height = PAGE_H;
      var ctx = canvas.getContext('2d');

      ctx.fillStyle = '#ffffff';
      ctx.fillRect(0, 0, PAGE_W, PAGE_H);

      /* 逐层绘制，保留图层透明度 */
      var layers = map.getViewport().querySelectorAll('.ol-layer');
      Array.prototype.forEach.call(layers, function (el) {
        var layerCanvas = el.querySelector('canvas');
        if (!layerCanvas) return;
        var opacity = parseFloat(el.style.opacity || '1');
        ctx.globalAlpha = isNaN(opacity) ? 1 : opacity;
        ctx.drawImage(layerCanvas, 0, TITLE_H, PAGE_W, PAGE_H - TITLE_H);
      });
      ctx.globalAlpha = 1;

      /* 标题与比例尺说明条 */
      ctx.fillStyle = '#16181d';
      ctx.font = '600 22px "PingFang SC","Microsoft YaHei",sans-serif';
      ctx.fillText('北京市中心城区要素分布', 40, 44);
      ctx.fillStyle = '#58606e';
      ctx.font = '13px "PingFang SC","Microsoft YaHei",sans-serif';
      var view = map.getView();
      var res = view.getResolution();
      ctx.fillText(
        '中心 ' + ol.proj.toLonLat(view.getCenter()).map(function (v) {
          return v.toFixed(5);
        }).join(', ') + '　分辨率 ' + res.toFixed(2) + ' m/px　' +
        mapSize[0] + ' × ' + mapSize[1] + ' 画布',
        40, 64
      );

      var url = canvas.toDataURL('image/png');
      var win = window.open('', '_blank');
      if (!win) {
        infoEl.textContent = '浏览器拦截了新窗口，请允许弹窗后重试';
        return;
      }
      win.document.write(
        '<!DOCTYPE html><html><head>
<meta name="robots" content="noindex,follow"><meta charset="utf-8"><title>地图导出</title>' +
        '<style>@page{size:A4 landscape;margin:0}' +
        'body{margin:0;font-family:sans-serif}' +
        'img{width:100%;display:block}' +
        '.hint{padding:10px 16px;color:#58606e;font-size:13px}</style></head><body>' +
        '<img src="' + url + '">' +
        '<p class="hint">按 Ctrl+P 选择「另存为 PDF」，纸张设为 A4 横向、边距为零即可得到单页 PDF。</p>' +
        '</body></html>'
      );
      win.document.close();
      infoEl.textContent = '已生成 ' + PAGE_W + ' × ' + PAGE_H + ' 版式，可在新窗口打印';
    });

    /* 触发一次同步渲染，让 rendercomplete 必定到来 */
    map.renderSync();
  });
})();
</script>
</body>
</html>