Generate and add a missing icon to the map | UNL Map JS Docs

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

Note

If you want to test this example, edit it in JSFiddle or CodePen and replace the "YOUR-OWN-API-KEY" and "YOUR-OWN-VPM-ID" placeholders with your actual api key and vpm id.

<!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/unl-map-js@0.1.5/lib/unl-map-js.js"></script>
<link href="https://unpkg.com/unl-map-js@0.1.5/lib/unl-map-js.css" rel="stylesheet" />
<link
href="https://unpkg.com/maplibre-gl@2.1.9/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 UnlSdk.Map({
container: "map",
apiKey: "YOUR-OWN-API-KEY",
vpmId: "YOUR-OWN-VPM-ID",
});
 
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>