This example uses OpenLayers v10.9.0. The latest is v.
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#### Data Tiles

datatiles 2

#####

Generating tile data from scratch.

This example generates RGBA tile data from scratch.

##### main.js

    import Map from 'ol/Map.js';
    import View from 'ol/View.js';
    import TileLayer from 'ol/layer/WebGLTile.js';
    import DataTile from 'ol/source/DataTile.js';

    const size = 256;

    const canvas = document.createElement('canvas');
    canvas.width = size;
    canvas.height = size;

    const context = canvas.getContext('2d', {willReadFrequently: true});
    context.strokeStyle = 'white';
    context.textAlign = 'center';
    context.font = '24px sans-serif';
    const lineHeight = 30;

    const map = new Map({
      target: 'map',
      layers: [
        new TileLayer({
          source: new DataTile({
            loader: function (z, x, y) {
              const half = size / 2;
              context.clearRect(0, 0, size, size);
              context.fillStyle = 'rgba(100, 100, 100, 0.5)';
              context.fillRect(0, 0, size, size);
              context.fillStyle = 'black';
              context.fillText(`z: ${z}`, half, half - lineHeight);
              context.fillText(`x: ${x}`, half, half);
              context.fillText(`y: ${y}`, half, half + lineHeight);
              context.strokeRect(0, 0, size, size);
              return context.getImageData(0, 0, size, size).data;
            },
            // disable opacity transition to avoid overlapping labels during tile loading
            transition: 0,
          }),
        }),
      ],
      view: new View({
        center: [0, 0],
        zoom: 0,
      }),
    });

##### index.html

    <!DOCTYPE html>
    <html lang="en">
      <head>
        <meta charset="UTF-8">
        <title>Data Tiles</title>
        <link rel="stylesheet" href="node_modules/ol/ol.css">
        <style>
          .map {
            width: 100%;
            height: 400px;
          }
        </style>
      </head>
      <body>
        <div id="map" class="map"></div>

        <script type="module" src="main.js"></script>
      </body>
    </html>

##### package.json

    {
      "name": "data-tiles",
      "dependencies": {
        "ol": "10.9.0"
      },
      "devDependencies": {
        "vite": "^3.2.3"
      },
      "scripts": {
        "start": "vite",
        "build": "vite build"
      }
    }