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Add an animated icon to the map

Add an animated icon to the map that was generated at runtime with the Canvas API.

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Add an animated icon to the map</title>
    <meta property="og:description" content="Add an animated icon to the map that was generated at runtime with the Canvas API." />
    <meta charset='utf-8'>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel='stylesheet' href='https://unpkg.com/maplibre-gl@4.4.0/dist/maplibre-gl.css' />
    <script src='https://unpkg.com/maplibre-gl@4.4.0/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'
    });

    const size = 200;

    // implementation of StyleImageInterface to draw a pulsing dot icon on the map
    // Search for StyleImageInterface in https://maplibre.org/maplibre-gl-js/docs/API/
    const pulsingDot = {
        width: size,
        height: size,
        data: new Uint8Array(size * size * 4),

        // get rendering context for the map canvas when layer is added to the map
        onAdd () {
            const canvas = document.createElement('canvas');
            canvas.width = this.width;
            canvas.height = this.height;
            this.context = canvas.getContext('2d');
        },

        // called once before every frame where the icon will be used
        render () {
            const duration = 1000;
            const t = (performance.now() % duration) / duration;

            const radius = (size / 2) * 0.3;
            const outerRadius = (size / 2) * 0.7 * t + radius;
            const context = this.context;

            // draw outer circle
            context.clearRect(0, 0, this.width, this.height);
            context.beginPath();
            context.arc(
                this.width / 2,
                this.height / 2,
                outerRadius,
                0,
                Math.PI * 2
            );
            context.fillStyle = `rgba(255, 200, 200,${1 - t})`;
            context.fill();

            // draw inner circle
            context.beginPath();
            context.arc(
                this.width / 2,
                this.height / 2,
                radius,
                0,
                Math.PI * 2
            );
            context.fillStyle = 'rgba(255, 100, 100, 1)';
            context.strokeStyle = 'white';
            context.lineWidth = 2 + 4 * (1 - t);
            context.fill();
            context.stroke();

            // update this image's data with data from the canvas
            this.data = context.getImageData(
                0,
                0,
                this.width,
                this.height
            ).data;

            // continuously repaint the map, resulting in the smooth animation of the dot
            map.triggerRepaint();

            // return `true` to let the map know that the image was updated
            return true;
        }
    };

    map.on('load', () => {
        map.addImage('pulsing-dot', pulsingDot, {pixelRatio: 2});

        map.addSource('points', {
            'type': 'geojson',
            'data': {
                'type': 'FeatureCollection',
                'features': [
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [0, 0]
                        }
                    }
                ]
            }
        });
        map.addLayer({
            'id': 'points',
            'type': 'symbol',
            'source': 'points',
            'layout': {
                'icon-image': 'pulsing-dot'
            }
        });
    });
</script>
</body>
</html>