Sentinel Hub Custom Script

<!--
  示例：Sentinel Hub 自定义脚本
  要点：把"脚本"抽象成可切换的像素表达式，切换后重绘影像
  依赖：OpenLayers 10.3.1 · jsDelivr CDN（底图 OSM，无 Key）
  替代：官方把 evalscript 发给服务端渲染，这里在浏览器里执行等价表达式
-->
<!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 自定义脚本</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:12px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar select,.bar input{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>脚本
    <select id="fx">
      <option value="gamma">gamma 1.8 提亮</option>
      <option value="ndvi">NDVI 分级着色</option>
      <option value="coast">海岸线增强</option>
      <option value="thermal">热异常叠加</option>
    </select>
  </label>
  <label>增益 <input type="range" id="gain" min="60" max="180" value="100" style="width:120px"></label>
  <span><b id="gv">1.00</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 fx = 'gamma';
  var gain = 1;

  function sample(lon, lat) {
    var r = 0.30 + 0.22 * Math.sin(lon * 2.1 + 0.5) * Math.cos(lat * 1.6);
    var g = 0.33 + 0.20 * Math.cos(lon * 1.7 + 0.2) * Math.sin(lat * 2.4);
    var b = 0.26 + 0.16 * Math.sin(lon * 3.1 + lat * 2.2);
    var nir = 0.44 + 0.28 * Math.cos(lon * 1.2 + 1.1) * Math.cos(lat * 1.8);
    return [r, g, b, nir];
  }

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

  /* 每个脚本就是一段像素表达式 */
  function apply(p) {
    var r = p[0], g = p[1], b = p[2], nir = p[3];
    if (fx === 'ndvi') {
      var nd = (nir - r) / (nir + r + 0.0001);
      if (nd < 0.1) return [clamp(0.62 + nd), clamp(0.58 + nd * 0.6), clamp(0.52)];
      if (nd < 0.35) return [clamp(0.85 - nd), clamp(0.80), clamp(0.42)];
      return [clamp(0.18), clamp(0.42 + nd * 0.5), clamp(0.20)];
    }
    if (fx === 'coast') {
      var idx = (b - r) * 3;
      if (idx > 0.15) return [clamp(0.15), clamp(0.45 + idx * 0.3), clamp(0.75)];
      return [clamp(r * 1.2 + 0.2), clamp(g * 1.1 + 0.2), clamp(b * 0.9 + 0.15)];
    }
    if (fx === 'thermal') {
      var heat = Math.max(0, nir - r - 0.12) * 2.4;
      return [clamp(heat + r * 0.5), clamp(0.35 + g * 0.4 - heat * 0.2), clamp(0.30 - heat * 0.1)];
    }
    var gam = 1 / 1.8;
    return [clamp(Math.pow(r, gam)), clamp(Math.pow(g, gam)), clamp(Math.pow(b, gam))];
  }

  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 p = sample(lon, lat);
        p = [p[0] * gain, p[1] * gain, p[2] * gain, p[3]];
        var c = apply(p);
        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([121.2, 31.0]), zoom: 8 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  document.getElementById('fx').addEventListener('change', function () {
    fx = this.value;
    source.changed();
  });

  document.getElementById('gain').addEventListener('input', function () {
    gain = Number(this.value) / 100;
    document.getElementById('gv').textContent = gain.toFixed(2);
    source.changed();
  });
})();
</script>
</body>
</html>