Imagery Cutout

<!--
  示例：影像矩形挖洞
  说明：底图中间挖掉一个矩形，露出下面另一张影像，边界正好对齐
  核心逻辑：layer.cutoutRectangle = Rectangle → 下层图层填补空洞
  依赖：CesiumJS 1.121 · 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>影像矩形挖洞</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%}
  .tip{position:absolute;left:12px;top:12px;z-index:5;
       background:rgba(23,28,35,.9);border:1px solid #2a313b;border-radius:6px;
       padding:8px 12px;font-size:12px;color:#a2a9b6;max-width:320px;line-height:1.6}

  .cesium-viewer-bottom .cesium-widget-credits,.cesium-viewer-animationContainer,
  .cesium-viewer-timelineContainer{display:none!important}
</style>
</head>
<body>
<div id="c"></div>
<div class="tip">中间方孔处显示的是下面那层影像，四周仍是原底图。</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('#1c2733');
  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;

  function makeImage(fill, label) {
    var c = document.createElement('canvas');
    c.width = 512; c.height = 512;
    var ctx = c.getContext('2d');
    ctx.fillStyle = fill; ctx.fillRect(0, 0, 512, 512);
    ctx.strokeStyle = 'rgba(255,255,255,0.35)';
    for (var i = 0; i < 512; i += 40) {
      ctx.beginPath(); ctx.moveTo(i, 0); ctx.lineTo(i, 512); ctx.stroke();
    }
    ctx.fillStyle = '#e8eef5';
    ctx.font = '600 40px sans-serif';
    ctx.fillText(label, 205, 265);
    return c.toDataURL('image/png');
  }

  var rect = Cesium.Rectangle.fromDegrees(115.9, 39.5, 116.9, 40.2);
  var hole = Cesium.Rectangle.fromDegrees(116.15, 39.65, 116.65, 39.95);

  /* 底层：被挖开后露出来的影像 */
  viewer.imageryLayers.addImageryProvider(
    new Cesium.SingleTileImageryProvider({
      url: makeImage('#1f4f46', '下层'),
      rectangle: rect
    })
  );

  /* 上层：中间挖洞 */
  var top = viewer.imageryLayers.addImageryProvider(
    new Cesium.SingleTileImageryProvider({
      url: makeImage('#3b4a5f', '上层'),
      rectangle: rect
    })
  );
  top.cutoutRectangle = hole;

  /* 洞的边框 */
  var c1 = Cesium.Cartesian3.fromDegrees(116.15, 39.65);
  var c2 = Cesium.Cartesian3.fromDegrees(116.65, 39.65);
  var c3 = Cesium.Cartesian3.fromDegrees(116.65, 39.95);
  var c4 = Cesium.Cartesian3.fromDegrees(116.15, 39.95);
  viewer.entities.add({
    polyline: {
      positions: [c1, c2, c3, c4, c1],
      width: 2,
      material: Cesium.Color.fromCssColorString('#ffb13d')
    }
  });
  viewer.camera.flyTo({
    destination: Cesium.Rectangle.fromDegrees(115.9, 39.5, 116.9, 40.2),
    duration: 0
  });
})();
</script>
</body>
</html>