Data Filter

<!--
  示例：数据过滤扩展
  核心逻辑：DataFilterExtension 在 GPU 上按数值区间裁剪实例，滑块只改 filterRange
  数据：页面内生成的 4000 个点，每个点带一个建成年份
  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>数据过滤扩展</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:14px;align-items:center;font-size:12px;color:#8b93a1;flex-wrap:wrap}
  .bar b{color:#58a6ff;font-weight:600}
  .bar input[type=range]{width:130px}
  #cv{flex:1 1 auto;min-height:0;width:100%}
</style>
</head>
<body>
<div class="bar">
  <span>总点数 <b id="n">—</b></span>
  <span>区间 <b id="rg">1970–2020</b></span>
  <label>起 <input id="a" type="range" min="1970" max="2020" step="1" value="1970"></label>
  <label>止 <input id="b" type="range" min="1970" max="2020" step="1" value="2020"></label>
  <span>过滤在着色器里完成，不改数据</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;
  }

  var cities = [
    [116.39, 39.90], [121.47, 31.23], [113.26, 23.12], [104.06, 30.57],
    [108.94, 34.34], [114.30, 30.59], [126.64, 45.75], [87.61, 43.82],
    [120.15, 30.28], [118.80, 32.06], [106.55, 29.56], [102.71, 25.04]
  ];

  var data = [];
  for (var i = 0; i < 4000; i++) {
    var c = cities[i % cities.length];
    data.push({
      lng: c[0] + (Math.random() + Math.random() - 1) * 2.4,
      lat: c[1] + (Math.random() + Math.random() - 1) * 1.8,
      /* 年份分布偏新，越接近 2020 的点越多 */
      year: Math.round(1970 + Math.pow(Math.random(), 0.6) * 50)
    });
  }
  document.getElementById('n').textContent = data.length.toLocaleString();

  var range = [1970, 2020];

  function build(filterRange) {
    return new deck.ScatterplotLayer({
      id: 'buildings',
      data: data,
      getPosition: function (d) { return [d.lng, d.lat]; },
      getRadius: 1.6,
      radiusUnits: 'pixels',
      radiusMinPixels: 1,
      getFillColor: function (d) {
        var t = (d.year - 1970) / 50;
        return [Math.round(80 + 175 * t), Math.round(180 - 60 * t), 220, 190];
      },
      getFilterValue: function (d) { return d.year; },
      filterRange: filterRange,
      extensions: [new deck.DataFilterExtension({ filterSize: 1 })],
      pickable: true
    });
  }

  var current = build(range);

  var deckgl = new deck.Deck({
    canvas: document.getElementById('cv'),
    width: '100%',
    height: '100%',
    initialViewState: {
      longitude: 108,
      latitude: 34,
      zoom: 3.4,
      pitch: 25,
      bearing: 0,
      maxPitch: 65
    },
    controller: true,
    layers: [current],
    getTooltip: function (info) {
      return info.object ? info.object.year + ' 年' : null;
    }
  });

  function apply() {
    var lo = parseInt(document.getElementById('a').value, 10);
    var hi = parseInt(document.getElementById('b').value, 10);
    /* 两个滑块可能交叉，这里保证区间方向正确 */
    if (lo > hi) { var t = lo; lo = hi; hi = t; }

    document.getElementById('rg').textContent = lo + '–' + hi;
    current = current.clone({ filterRange: [lo, hi] });
    deckgl.setProps({ layers: [current] });
  }

  document.getElementById('a').addEventListener('input', apply);
  document.getElementById('b').addEventListener('input', apply);

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