Canvas Tiles

<!--
  说明：Canvas 瓦片的中文示例，数据在页面内生成，可独立运行。
  核心逻辑：tileUrlFunction 生成 canvas + toDataURL + TileImage 渲染
  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>Canvas 瓦片</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:10px;align-items:center;flex-wrap:wrap;font-size:12px;color:#58606e}
  .bar label{display:flex;gap:5px;align-items:center;cursor:pointer}
  .bar button{font:inherit;padding:3px 9px;border:1px solid #c9ced6;background:#fff;
       border-radius:5px;cursor:pointer;color:#333}
  .bar button:hover{background:#eef2f8}
  .bar input[type=range]{width:110px;vertical-align:middle}
  .bar input[type=text]{font:inherit;padding:2px 6px;border:1px solid #c9ced6;border-radius:4px}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3;position:relative}
  .panel{flex:0 0 auto;max-height:34%;overflow:auto;padding:8px 12px;font-size:12px;
       background:#fff;border-top:1px solid #e3e6ea;color:#3d4451}
  .panel pre{margin:0;font-family:Consolas,"Courier New",monospace;font-size:11px;
       white-space:pre-wrap;word-break:break-all;line-height:1.5}
  .ol-attribution{font-size:11px}

</style>
</head>
<body>
<div class="bar">
<label><input type="checkbox" id="base" checked> 叠加 OSM 底图</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') {
    var errBox = document.getElementById('map');
    if (errBox) {
      errBox.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;
  var resolutions = [];
  (function () {
    var res = 156543.03392804097;
    for (var z = 0; z <= 8; z++) { resolutions.push(res); res = res / 2; }
  })();

  var grid = new ol.tilegrid.TileGrid({
    origin: ol.extent.getTopLeft(ol.proj.get('EPSG:3857').getExtent()),
    resolutions: resolutions,
    tileSize: 256
  });

  var info = document.getElementById('info');
  var generated = 0;

  function tileUrl(tileCoord) {
    if (!tileCoord) { return ''; }
    var z = tileCoord[0];
    var x = tileCoord[1];
    var y = tileCoord[2];
    var c = document.createElement('canvas');
    c.width = c.height = 256;
    var ctx = c.getContext('2d');
    var hue = Math.abs(z * 47 + x * 13 + y * 29) % 360;

    ctx.fillStyle = 'hsl(' + hue + ',42%,93%)';
    ctx.fillRect(0, 0, 256, 256);
    ctx.font = 'bold 12px monospace';
    ctx.fillStyle = 'hsl(' + hue + ',45%,42%)';
    ctx.fillText('256 × 256 tile', 16, 24);

    ctx.font = 'bold 26px monospace';
    ctx.fillStyle = '#2b3444';
    ctx.fillText('z ' + z, 16, 70);
    ctx.fillText('x ' + x, 16, 108);
    ctx.fillText('y ' + y, 16, 146);

    ctx.strokeStyle = 'hsl(' + hue + ',55%,62%)';
    ctx.lineWidth = 2;
    ctx.strokeRect(1, 1, 254, 254);

    generated++;
    info.textContent = '已生成 ' + generated + ' 张瓦片 · 当前缩放 ' +
      (map ? map.getView().getZoom().toFixed(1) : '—');
    return c.toDataURL('image/png');
  }

  var base = 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'})});
  var canvasTiles = new ol.layer.Tile({
    source: new ol.source.TileImage({
      projection: 'EPSG:3857',
      tileGrid: grid,
      tileUrlFunction: tileUrl
    }),
    opacity: 0.88
  });

  var map = new ol.Map({
    target: 'map',
    layers: [base, canvasTiles],
    view: new ol.View({center: fromLonLat([104, 35]), zoom: 3}),
    controls: ol.control.defaults.defaults({attribution: false, zoom: true, rotate: false})
  });

  document.getElementById('base').addEventListener('change', function () {
    base.setVisible(this.checked);
  });
})();
</script>
</body>
</html>