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Generate and add a missing icon to the map

Dynamically generate a missing icon at runtime and add it to the map.

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Generate and add a missing icon to the map</title>
    <meta property="og:description" content="Dynamically generate a missing icon at runtime and add it to the map." />
    <meta charset='utf-8'>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel='stylesheet' href='https://unpkg.com/maplibre-gl@5.0.1/dist/maplibre-gl.css' />
    <script src='https://unpkg.com/maplibre-gl@5.0.1/dist/maplibre-gl.js'></script>
    <style>
        body { margin: 0; padding: 0; }
        html, body, #map { height: 100%; }
    </style>
</head>
<body>
<div id="map"></div>

<script>
    const map = new maplibregl.Map({
        container: 'map',
        style:
            'https://api.maptiler.com/maps/streets/style.json?key=get_your_own_OpIi9ZULNHzrESv6T2vL'
    });

    map.on('styleimagemissing', (e) => {
        const id = e.id; // id of the missing image

        // check if this missing icon is one this function can generate
        const prefix = 'square-rgb-';
        if (id.indexOf(prefix) !== 0) return;

        // extract the color from the id
        const rgb = id.replace(prefix, '').split(',').map(Number);

        const width = 64; // The image will be 64 pixels square
        const bytesPerPixel = 4; // Each pixel is represented by 4 bytes: red, green, blue, and alpha.
        const data = new Uint8Array(width * width * bytesPerPixel);

        for (let x = 0; x < width; x++) {
            for (let y = 0; y < width; y++) {
                const offset = (y * width + x) * bytesPerPixel;
                data[offset + 0] = rgb[0]; // red
                data[offset + 1] = rgb[1]; // green
                data[offset + 2] = rgb[2]; // blue
                data[offset + 3] = 255; // alpha
            }
        }

        map.addImage(id, {width, height: width, data});
    });

    map.on('load', () => {
        map.addSource('points', {
            'type': 'geojson',
            'data': {
                'type': 'FeatureCollection',
                'features': [
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [0, 0]
                        },
                        'properties': {
                            'color': '255,0,0'
                        }
                    },
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [50, 0]
                        },
                        'properties': {
                            'color': '255,209,28'
                        }
                    },
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [-50, 0]
                        },
                        'properties': {
                            'color': '242,127,32'
                        }
                    }
                ]
            }
        });

        map.addLayer({
            'id': 'points',
            'type': 'symbol',
            'source': 'points',
            'layout': {
                'icon-image': ['concat', 'square-rgb-', ['get', 'color']]
            }
        });
    });
</script>
</body>
</html>