Heatmap

<!--
  示例：deck.gl 热力图
  要点：HeatmapLayer 用核密度把四点二万个点压成连续密度场，核半径可实时调节
  依赖：deck.gl 9.0 · 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>热力图</title>
<style>
  html,body{height:100%;margin:0;background:#0d1117}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif;color:#e6e8ec}
  .bar{position:relative;z-index:5;flex:0 0 auto;padding:8px 12px;background:#161b22;border-bottom:1px solid #252c36;
       display:flex;gap:18px;align-items:center;font-size:12px;color:#8b93a1;flex-wrap:wrap}
  .bar b{color:#58a6ff;font-weight:600}
  .bar input[type=range]{width:150px;accent-color:#4f9ef8}
  #cv{flex:1 1 auto;min-height:0;width:100%}
</style>
</head>
<body>
<div class="bar">
  <span>点数 <b id="n">—</b></span>
  <span>核半径 <b id="rv">44</b> px</span>
  <label>半径 <input type="range" id="radius" min="12" max="80" step="2" value="44"></label>
  <span>拖拽旋转 · 滚轮缩放</span>
</div>
<canvas id="cv"></canvas>
<script src="https://cdn.jsdelivr.net/npm/deck.gl@9.0.35/dist.min.js"></script>
<script>
(function () {
  'use strict';

  if (typeof deck === 'undefined') {
    document.body.innerHTML =
      '<div style="padding:24px;color:#ff8c74">deck.gl 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  /* 五个聚集中心，模拟不同强度的活动区域 */
  var centers = [
    [121.470, 31.232, 15000, 0.26],
    [121.620, 31.120, 9000, 0.18],
    [121.320, 31.300, 7000, 0.15],
    [121.545, 31.345, 6000, 0.12],
    [121.405, 31.055, 5000, 0.14]
  ];

  var points = [];
  function gauss() {
    var u = 1 - Math.random();
    var v = Math.random();
    return Math.sqrt(-2 * Math.log(u)) * Math.cos(2 * Math.PI * v) * 0.38;
  }

  for (var i = 0; i < centers.length; i++) {
    var c = centers[i];
    for (var j = 0; j < c[2]; j++) {
      points.push({
        lng: c[0] + gauss() * c[3],
        lat: c[1] + gauss() * c[3] * 0.8,
        w: 0.55 + Math.random() * 0.75
      });
    }
  }

  document.getElementById('n').textContent = points.length.toLocaleString();

  var colorRange = [
    [8, 24, 58, 0],
    [22, 68, 130, 110],
    [32, 130, 190, 175],
    [96, 200, 190, 205],
    [248, 208, 88, 225],
    [243, 120, 48, 240],
    [208, 34, 45, 255]
  ];

  var radiusPixels = 44;

  function buildLayer() {
    return new deck.HeatmapLayer({
      id: 'density',
      data: points,
      getPosition: function (d) { return [d.lng, d.lat]; },
      getWeight: function (d) { return d.w; },
      radiusPixels: radiusPixels,
      intensity: 1.15,
      threshold: 0.04,
      aggregation: 'SUM',
      colorRange: colorRange
    });
  }

  var deckgl = new deck.Deck({
    canvas: 'cv',
    width: '100%',
    height: '100%',
    initialViewState: {
      longitude: 121.46,
      latitude: 31.20,
      zoom: 10.4,
      pitch: 0,
      bearing: 0
    },
    controller: true,
    layers: [buildLayer()]
  });

  document.getElementById('radius').addEventListener('input', function (e) {
    radiusPixels = Number(e.target.value);
    document.getElementById('rv').textContent = radiusPixels;
    deckgl.setProps({ layers: [buildLayer()] });
  });

  window.__deck = deckgl;
})();
</script>
</body>
</html>