MapLibreMapLibre GL JS DocsExamplesGenerate and add a missing icon to the map

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>
<head>
<meta charset="utf-8" />
<title>Generate and add a missing icon to the map</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no" />
<script src="https://unpkg.com/[email protected]/dist/maplibre-gl.js"></script>
<link href="https://unpkg.com/[email protected]/dist/maplibre-gl.css" rel="stylesheet" />
<style>
body { margin: 0; padding: 0; }
#map { position: absolute; top: 0; bottom: 0; width: 100%; }
</style>
</head>
<body>
<div id="map"></div>
<script>
var map = new maplibregl.Map({
container: 'map',
style:
'https://api.maptiler.com/maps/streets/style.json?key=get_your_own_OpIi9ZULNHzrESv6T2vL'
});
map.on('styleimagemissing', function (e) {
var id = e.id; // id of the missing image
// check if this missing icon is one this function can generate
var prefix = 'square-rgb-';
if (id.indexOf(prefix) !== 0) return;
// extract the color from the id
var rgb = id.replace(prefix, '').split(',').map(Number);
var width = 64; // The image will be 64 pixels square
var bytesPerPixel = 4; // Each pixel is represented by 4 bytes: red, green, blue, and alpha.
var data = new Uint8Array(width * width * bytesPerPixel);
for (var x = 0; x < width; x++) {
for (var y = 0; y < width; y++) {
var 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: width, height: width, data: data });
});
map.on('load', function () {
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>