Drag and Drop Image Vector

<!--
  示例：拖放影像矢量渲染
  核心逻辑：DragAndDrop 解析 GeoJSON 后写入 VectorImage 图层，整层一次性栅格化
  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>拖放影像矢量渲染</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:4px 10px;border:1px solid #c9d0da;border-radius:5px;
              background:#fff;color:#1f2a37;cursor:pointer}
  #info{margin-left:auto}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <span>拖入 GeoJSON 文件</span>
  <button id="sample">加载内置示例</button>
  <button id="clear">清空</button>
  <span id="info">—</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 sampleJson = {
    type: 'FeatureCollection',
    features: [
      { type: 'Feature', properties: { name: '中轴线' },
        geometry: { type: 'LineString',
          coordinates: [[116.391, 39.85], [116.393, 39.90], [116.396, 39.95]] } },
      { type: 'Feature', properties: { name: '二环北段' },
        geometry: { type: 'LineString',
          coordinates: [[116.35, 39.95], [116.40, 39.96], [116.45, 39.95]] } },
      { type: 'Feature', properties: { name: '中心点' },
        geometry: { type: 'Point', coordinates: [116.391, 39.907] } }
    ]
  };

  var source = new ol.source.Vector();

  var LayerClass = ol.layer.VectorImage || ol.layer.Vector;

  var layer = new LayerClass({
    source: source,
    style: function (feature) {
      var geom = feature.getGeometry();
      if (geom instanceof ol.geom.Point) {
        return new ol.style.Style({
          image: new ol.style.Circle({
            radius: 7,
            fill: new ol.style.Fill({ color: '#e2483c' }),
            stroke: new ol.style.Stroke({ color: '#ffffff', width: 2 })
          }),
          text: new ol.style.Text({
            text: feature.get('name') || '',
            font: '600 12px sans-serif',
            offsetY: -15,
            fill: new ol.style.Fill({ color: '#16181d' }),
            stroke: new ol.style.Stroke({ color: '#ffffff', width: 3 })
          })
        });
      }
      return new ol.style.Style({
        stroke: new ol.style.Stroke({ color: '#1f5fd0', width: 3, lineCap: 'round' }),
        text: new ol.style.Text({
          text: feature.get('name') || '',
          font: '600 12px sans-serif',
          overflow: true,
          fill: new ol.style.Fill({ color: '#123b78' }),
          stroke: new ol.style.Stroke({ color: '#ffffff', width: 3 })
        })
      });
    }
  });

  var format = new ol.format.GeoJSON({
    dataProjection: 'EPSG:4326',
    featureProjection: 'EPSG:3857'
  });

  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'}) }), layer],
    view: new ol.View({ center: fromLonLat([116.391, 39.907]), zoom: 12, minZoom: 2, maxZoom: 19 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

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

  var dragAndDrop = new ol.interaction.DragAndDrop({ format: format });
  dragAndDrop.on('addfeatures', function (evt) {
    if (!evt.features.length) return;
    source.addFeatures(evt.features);
    map.getView().fit(source.getExtent(), { padding: [80, 80, 80, 80], duration: 500 });
    info.textContent = '加入 ' + evt.features.length + ' 个要素 · 当前 ' + source.getFeatures().length + ' 个';
  });
  map.addInteraction(dragAndDrop);

  document.getElementById('sample').addEventListener('click', function () {
    var feats = format.readFeatures(sampleJson);
    source.clear();
    source.addFeatures(feats);
    map.getView().fit(source.getExtent(), { padding: [90, 90, 90, 90], duration: 500 });
    info.textContent = '已加载内置示例 ' + feats.length + ' 个要素';
  });

  document.getElementById('clear').addEventListener('click', function () {
    source.clear();
    info.textContent = '已清空';
  });
})();
</script>
</body>
</html>