Generate and add a missing icon to the map

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


npm install --save @maptiler/sdk

main.js

import { Map, MapStyle, config } from '@maptiler/sdk';
import '@maptiler/sdk/dist/maptiler-sdk.css';

config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';
const map = new Map({
    container: 'map',
    style: MapStyle.STREETS,
    center: [0, 0],
    zoom: 2
});

map.on('styleimagemissing', function (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: 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']]
        }
    });
});

index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="robots" content="noindex">
  <title>Generate and add a missing icon to the map</title>
  <link rel="stylesheet" href="./style.css">
</head>
<body>
  <div id="map"></div>
  <script type="module" src="./main.js"></script>
</body>
</html>

style.css

body {margin: 0; padding: 0;}
#map {position: absolute; top: 0; bottom: 0; width: 100%;}

<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Generate and add a missing icon to the map</title>
<script src="https://cdn.maptiler.com/maptiler-sdk-js/v4.1.0/maptiler-sdk.umd.min.js"></script>
<link href="https://cdn.maptiler.com/maptiler-sdk-js/v4.1.0/maptiler-sdk.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>
    maptilersdk.config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';
    const map = new maptilersdk.Map({
        container: 'map',
        style: maptilersdk.MapStyle.STREETS,
        center: [0, 0],
        zoom: 2
    });

    map.on('styleimagemissing', function (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: 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>