Cog Custom Client

<!--
  说明：自定义瓦片加载函数的中文示例，数据在页面内生成，可独立运行。
  核心逻辑：tileLoadFunction 自定义加载 + tile.getImage() + 请求耗时统计
  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>自定义瓦片加载函数</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">
<span id="info">—</span>
<button id="reset" type="button">重置统计</button>
</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 grid = ol.tilegrid.createXYZ({maxZoom: 19});
  var requests = 0;
  var completed = 0;
  var totalMs = 0;
  var info = document.getElementById('info');

  function report() {
    var avg = completed ? (totalMs / completed).toFixed(0) : '0';
    info.textContent = '请求 ' + requests + ' 次 · 完成 ' + completed + ' 次 · 平均 ' + avg + ' ms';
  }

  function drawTile(z, x, y) {
    var c = document.createElement('canvas');
    c.width = c.height = 256;
    var ctx = c.getContext('2d');
    var hue = Math.abs(z * 31 + x * 7 + y * 17) % 360;
    ctx.fillStyle = 'hsl(' + hue + ',35%,92%)';
    ctx.fillRect(0, 0, 256, 256);
    ctx.strokeStyle = 'hsl(' + hue + ',45%,55%)';
    ctx.lineWidth = 2;
    ctx.strokeRect(1, 1, 254, 254);
    ctx.fillStyle = '#2b3444';
    ctx.font = 'bold 20px monospace';
    ctx.fillText('z' + z, 14, 36);
    ctx.fillText('x' + x, 14, 64);
    ctx.fillText('y' + y, 14, 92);
    ctx.font = '12px monospace';
    ctx.fillText('自定义加载器', 14, 120);
    return c.toDataURL('image/png');
  }

  var source = new ol.source.TileImage({
    projection: 'EPSG:3857',
    tileGrid: grid,
    tileUrlFunction: function (tileCoord) {
      if (!tileCoord) { return ''; }
      return tileCoord[0] + '/' + tileCoord[1] + '/' + tileCoord[2];
    },
    tileLoadFunction: function (tile, url) {
      var started = Date.now();
      requests++;
      report();
      var parts = url.split('/');
      var delay = 80 + Math.random() * 260;

      setTimeout(function () {
        var img = tile.getImage();
        img.onload = function () {
          completed++;
          totalMs += Date.now() - started;
          report();
        };
        img.onerror = function () {
          completed++;
          report();
        };
        img.src = drawTile(+parts[0], +parts[1], +parts[2]);
      }, delay);
    }
  });

  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.Tile({source: source, opacity: 0.88})
    ],
    view: new ol.View({center: fromLonLat([116.4, 39.9]), zoom: 4}),
    controls: ol.control.defaults.defaults({attribution: false, zoom: true, rotate: false})
  });

  document.getElementById('reset').addEventListener('click', function () {
    requests = 0;
    completed = 0;
    totalMs = 0;
    report();
  });

  report();
})();
</script>
</body>
</html>