This example uses OpenLayers v10.9.0. The latest is v.
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#### GeoTIFF with Overviews

cog 15 overview 3

#####

Rendering a GeoTIFF with external overviews as a layer.

In some cases, a GeoTIFF may have external overviews. This example uses the `overviews` property to provide URL for a file containing external overviews.

##### main.js

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

    const source = new GeoTIFF({
      sources: [
        {
          url: 'https://openlayers.org/data/raster/no-overviews.tif',
          overviews: ['https://openlayers.org/data/raster/no-overviews.ovr.tif'],
        },
      ],
    });

    const map = new Map({
      target: 'map',
      layers: [
        new TileLayer({
          source: source,
        }),
      ],
      view: source.getView(),
    });

##### index.html

    <!DOCTYPE html>
    <html lang="en">
      <head>
        <meta charset="UTF-8">
        <title>GeoTIFF with Overviews</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": "cog-overviews",
      "dependencies": {
        "ol": "10.9.0"
      },
      "devDependencies": {
        "vite": "^3.2.3"
      },
      "scripts": {
        "start": "vite",
        "build": "vite build"
      }
    }