Icon Negative

<!--
  说明：图标反色处理
  核心逻辑：Canvas getImageData 逐通道取反，生成反色 Icon 的 data URL
  依赖：OpenLayers 10.3.1 · 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>图标反色处理</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}
  .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}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label><input type="checkbox" id="neg"> 反色</label>
  <span id="info">—</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 (typeof ol === 'undefined') {
    document.getElementById('map').innerHTML =
      '<div style="padding:20px;color:#b42318">OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  var fromLonLat = ol.proj.fromLonLat;

  function baseCanvas() {
    var canvas = document.createElement('canvas');
    canvas.width = 36;
    canvas.height = 36;
    var ctx = canvas.getContext('2d');
    ctx.beginPath();
    ctx.arc(18, 18, 15, 0, Math.PI * 2);
    ctx.fillStyle = '#1f5fd0';
    ctx.fill();
    ctx.strokeStyle = '#ffffff';
    ctx.lineWidth = 3;
    ctx.stroke();
    ctx.beginPath();
    ctx.moveTo(11, 18);
    ctx.lineTo(25, 18);
    ctx.moveTo(18, 11);
    ctx.lineTo(18, 25);
    ctx.strokeStyle = '#ffffff';
    ctx.lineWidth = 2.5;
    ctx.stroke();
    return canvas;
  }

  function invert(canvas) {
    var ctx = canvas.getContext('2d');
    var img = ctx.getImageData(0, 0, canvas.width, canvas.height);
    for (var i = 0; i < img.data.length; i += 4) {
      img.data[i] = 255 - img.data[i];
      img.data[i + 1] = 255 - img.data[i + 1];
      img.data[i + 2] = 255 - img.data[i + 2];
    }
    ctx.putImageData(img, 0, 0);
    return canvas.toDataURL();
  }

  var normalUrl = baseCanvas().toDataURL();
  var negativeUrl = invert(baseCanvas());

  var negative = false;

  var features = [
    [116.34, 39.92], [116.44, 39.92], [116.39, 39.86]
  ].map(function (p) {
    return new ol.Feature({ geometry: new ol.geom.Point(fromLonLat(p)) });
  });

  function styleFn() {
    return new ol.style.Style({
      image: new ol.style.Icon({
        src: negative ? negativeUrl : normalUrl,
        anchor: [0.5, 0.5]
      })
    });
  }

  var layer = new ol.layer.Vector({
    source: new ol.source.Vector({ features: features }),
    style: styleFn
  });

  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'}) }), layer],
    view: new ol.View({ center: fromLonLat([116.39, 39.90]), zoom: 13, minZoom: 2, maxZoom: 19 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  var info = document.getElementById('info');

  document.getElementById('neg').addEventListener('change', function () {
    negative = this.checked;
    layer.changed();
    info.textContent = negative ? '当前：反色图标' : '当前：原色图标';
  });

  info.textContent = '当前：原色图标';
})();
</script>
</body>
</html>