Postprocess Color

<!--
  示例：自己写一个调色后处理阶段
  要点：PostProcessStage 用 colorTexture 采样上一帧，按 uMode 做灰度、反相或棕褐
  依赖：CesiumJS 1.121 · jsDelivr CDN，着色器内联在页面里
-->
<!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>自定义调色后处理</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Widgets/widgets.css">
<style>
  html,body{height:100%;margin:0}
  body{background:#0e1116;color:#e6e8ec;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif}
  #c{height:100%}
  .hud{position:absolute;left:12px;top:12px;z-index:5;background:rgba(23,28,35,.92);
       border:1px solid #2a313b;border-radius:6px;padding:9px 12px;font-size:12px;
       color:#a2a9b6;width:250px}
  .hud b{color:#e6e8ec;font-weight:600}
  .hud .row{margin-top:7px}
  input[type=range]{width:100%}
  select{font:inherit;font-size:12px;background:#1d232b;color:#cfd6e2;
       border:1px solid #343b46;border-radius:4px;padding:2px 4px;width:100%}
  .hud button{font:inherit;font-size:12px;padding:3px 9px;border-radius:4px;cursor:pointer;
       border:1px solid #343b46;background:#1d232b;color:#cfd6e2;margin-top:8px}
  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="hud">
  <div><b>调色后处理</b></div>
  <div class="row">强度 <span id="aVal">0.60</span></div>
  <div class="row"><input id="amt" type="range" min="0" max="1" step="0.05" value="0.6"></div>
  <div class="row">模式</div>
  <div class="row">
    <select id="mode">
      <option value="0">灰度</option>
      <option value="1">反相</option>
      <option value="2">棕褐</option>
    </select>
  </div>
  <div class="row"><button id="toggle">关闭后处理</button></div>
</div>
<script src="https://cdn.jsdelivr.net/npm/cesium@1.121.0/Build/Cesium/Cesium.js"></script>
<script>
(function () {
  'use strict';

  var viewer = new Cesium.Viewer('c', {
    baseLayer: false,
    baseLayerPicker: false, geocoder: false, homeButton: false,
    sceneModePicker: false, navigationHelpButton: false,
    animation: false, timeline: false, fullscreenButton: false,
    infoBox: false, selectionIndicator: false
  });

  var scene = viewer.scene;
  scene.globe.baseColor = Cesium.Color.fromCssColorString('#1f2f40');
  scene.backgroundColor = Cesium.Color.fromCssColorString('#0e1116');
  scene.skyBox.show = false;
  scene.sun.show = false;
  scene.moon.show = false;
  if (scene.skyAtmosphere) scene.skyAtmosphere.show = false;

  /* 三色方块 + 地面条带，方便判断调色是否生效 */
  var COLORS = ['#4d9bff', '#ffb13d', '#5fd0a8', '#e35d6a'];
  COLORS.forEach(function (c, i) {
    viewer.entities.add({
      position: Cesium.Cartesian3.fromDegrees(116.374 + i * 0.010, 39.904, 130),
      box: {
        dimensions: new Cesium.Cartesian3(160, 160, 260),
        material: Cesium.Color.fromCssColorString(c)
      }
    });
  });
  viewer.entities.add({
    position: Cesium.Cartesian3.fromDegrees(116.389, 39.886, 0),
    box: {
      dimensions: new Cesium.Cartesian3(4600, 120, 10),
      material: Cesium.Color.fromCssColorString('#8fa3b8')
    }
  });

  var SHADER = [
    'uniform sampler2D colorTexture;',
    'uniform float uAmount;',
    'uniform float uMode;',
    'in vec2 v_textureCoordinates;',
    '',
    'void main() {',
    '  vec4 color = texture(colorTexture, v_textureCoordinates);',
    '  float gray = dot(color.rgb, vec3(0.299, 0.587, 0.114));',
    '  vec3 target = uMode < 0.5',
    '    ? vec3(gray)',
    '    : (uMode < 1.5',
    '      ? vec3(1.0) - color.rgb',
    '      : vec3(',
    '          dot(color.rgb, vec3(0.393, 0.769, 0.189)),',
    '          dot(color.rgb, vec3(0.349, 0.686, 0.168)),',
    '          dot(color.rgb, vec3(0.272, 0.534, 0.131))',
    '        ));',
    '  out_FragColor = vec4(mix(color.rgb, target, uAmount), color.a);',
    '}'
  ].join('\n');

  var stage = scene.postProcessStages.add(new Cesium.PostProcessStage({
    fragmentShader: SHADER,
    uniforms: {
      uAmount: 0.6,
      uMode: 0
    }
  }));

  document.getElementById('amt').addEventListener('input', function () {
    stage.uniforms.uAmount = parseFloat(this.value);
    document.getElementById('aVal').textContent = parseFloat(this.value).toFixed(2);
  });

  document.getElementById('mode').addEventListener('change', function () {
    stage.uniforms.uMode = parseFloat(this.value);
  });

  document.getElementById('toggle').addEventListener('click', function () {
    stage.enabled = !stage.enabled;
    this.textContent = stage.enabled ? '关闭后处理' : '开启后处理';
  });

  viewer.camera.flyTo({
    destination: Cesium.Cartesian3.fromDegrees(116.386, 39.888, 1900),
    orientation: {
      heading: 0,
      pitch: Cesium.Math.toRadians(-22),
      roll: 0
    },
    duration: 0
  });
})();
</script>
</body>
</html>