Sentinel Hub

<!--
  示例：Sentinel Hub 影像
  要点：ImageCanvas 按波段组合渲染，切换合成方式即时重绘
  依赖：OpenLayers 10.3.1 · jsDelivr CDN（底图 OSM，无 Key）
  替代：官方经 Sentinel Hub 服务取多波段影像，这里用页面内生成的合成波段
-->
<!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>Sentinel Hub 影像</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;color:#16181d}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:14px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar select{font-size:12px;padding:2px 4px}
  .bar b{color:#16181d;font-weight:600}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label>波段组合
    <select id="combo">
      <option value="true">真彩色 R/G/B</option>
      <option value="false">假彩色 NIR/R/G</option>
      <option value="ndvi">植被指数 NDVI</option>
      <option value="swir">短波红外增强</option>
    </select>
  </label>
  <span>当前 <b id="name">真彩色</b></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 (!window.ol) {
    document.getElementById('map').textContent = 'OpenLayers 加载失败，请检查 cdn.jsdelivr.net 是否可访问';
    return;
  }

  var R = 6378137;
  var DEG = 180 / Math.PI;
  var combo = 'true';

  /* 四波段：红、绿、蓝、近红外，均为 0..1 的合成值 */
  function bands(lon, lat) {
    var r = 0.32 + 0.20 * Math.sin(lon * 2.3 + 0.6) * Math.cos(lat * 2.1);
    var g = 0.34 + 0.18 * Math.cos(lon * 1.9) * Math.sin(lat * 2.6 + 0.3);
    var b = 0.28 + 0.14 * Math.sin(lon * 3.7 + lat * 2.9);
    var nir = 0.46 + 0.26 * Math.cos(lon * 1.3 + 1.2) * Math.cos(lat * 1.7);
    return { r: r, g: g, b: b, nir: nir };
  }

  function clamp(v) { return Math.max(0, Math.min(255, Math.round(v * 255))); }

  function renderPixel(s) {
    if (combo === 'false') {
      return [clamp(s.nir), clamp(s.r), clamp(s.g)];
    }
    if (combo === 'ndvi') {
      var nd = (s.nir - s.r) / (s.nir + s.r + 0.0001);
      if (nd > 0) return [clamp(0.25 * (1 - nd)), clamp(0.45 + 0.45 * nd), clamp(0.28)];
      return [clamp(0.55 - nd * 0.4), clamp(0.55 + nd * 0.25), clamp(0.5)];
    }
    if (combo === 'swir') {
      return [clamp(s.r * 1.4), clamp(s.g * 0.8), clamp(s.b * 0.6 + s.nir * 0.4)];
    }
    return [clamp(s.r * 1.6), clamp(s.g * 1.5), clamp(s.b * 1.7)];
  }

  var canvasFunction = function (extent, resolution, pixelRatio, size) {
    var w = Math.max(1, Math.round(size[0]));
    var h = Math.max(1, Math.round(size[1]));
    var canvas = document.createElement('canvas');
    canvas.width = w;
    canvas.height = h;
    var ctx = canvas.getContext('2d');
    var img = ctx.createImageData(w, h);
    var sx = (extent[2] - extent[0]) / w;
    var sy = (extent[3] - extent[1]) / h;

    for (var y = 0; y < h; y++) {
      var my = extent[3] - (y + 0.5) * sy;
      var lat = (2 * Math.atan(Math.exp(my / R)) - Math.PI / 2) * DEG;
      for (var x = 0; x < w; x++) {
        var lon = (extent[0] + (x + 0.5) * sx) / R * DEG;
        var c = renderPixel(bands(lon, lat));
        var i = (y * w + x) * 4;
        img.data[i] = c[0];
        img.data[i + 1] = c[1];
        img.data[i + 2] = c[2];
        img.data[i + 3] = 255;
      }
    }
    ctx.putImageData(img, 0, 0);
    return canvas;
  };

  var source = new ol.source.ImageCanvas({ canvasFunction: canvasFunction });

  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.Image({ source: source, opacity: 0.85 })
    ],
    view: new ol.View({ center: ol.proj.fromLonLat([118.8, 32.0]), zoom: 8 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  var NAMES = { 'true': '真彩色', 'false': '假彩色', ndvi: '植被指数', swir: '短波红外增强' };

  document.getElementById('combo').addEventListener('change', function () {
    combo = this.value;
    document.getElementById('name').textContent = NAMES[combo];
    source.changed();
  });
})();
</script>
</body>
</html>