Add a stretchable image to the map

Use a stretchable image as a background for text. Stretchable images allow some parts of the image to stretch while keeping other parts, such as corners, at a constant size. Set the layout property 'icon-text-fit': 'both' to use the image as background for the text.


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, 
    zoom: 0.1
});

const images = {
    'popup': 'https://docs.maptiler.com/sdk-js/assets/popup.png',
    'popup-debug':
        'https://docs.maptiler.com/sdk-js/assets/popup_debug.png'
};

map.on('load', async () => {
    const debugPopup = await map.loadImage(images['popup-debug']);
    const popup = await map.loadImage(images['popup']);
    map.addImage('popup-debug', debugPopup.data, {
        // The two (blue) columns of pixels that can be stretched horizontally:
        //   - the pixels between x: 25 and x: 55 can be stretched
        //   - the pixels between x: 85 and x: 115 can be stretched.
        stretchX: [
            [25, 55],
            [85, 115]
        ],
        // The one (red) row of pixels that can be stretched vertically:
        //   - the pixels between y: 25 and y: 100 can be stretched
        stretchY: [[25, 100]],
        // This part of the image that can contain text ([x1, y1, x2, y2]):
        content: [25, 25, 115, 100],
        // This is a high-dpi image:
        pixelRatio: 2
    });
    map.addImage('popup', popup.data, {
        stretchX: [
            [25, 55],
            [85, 115]
        ],
        stretchY: [[25, 100]],
        content: [25, 25, 115, 100],
        pixelRatio: 2
    });

    map.addSource('points', {
        'type': 'geojson',
        'data': {
            'type': 'FeatureCollection',
            'features': [
                {
                    'type': 'Feature',
                    'geometry': {
                        'type': 'Point',
                        'coordinates': [40, -30]
                    },
                    'properties': {
                        'image-name': 'popup-debug',
                        'name': 'Line 1\nLine 2\nLine 3'
                    }
                },
                {
                    'type': 'Feature',
                    'geometry': {
                        'type': 'Point',
                        'coordinates': [40, 30]
                    },
                    'properties': {
                        'image-name': 'popup',
                        'name': 'Line 1\nLine 2\nLine 3'
                    }
                },
                {
                    'type': 'Feature',
                    'geometry': {
                        'type': 'Point',
                        'coordinates': [-40, -30]
                    },
                    'properties': {
                        'image-name': 'popup-debug',
                        'name': 'One longer line'
                    }
                },
                {
                    'type': 'Feature',
                    'geometry': {
                        'type': 'Point',
                        'coordinates': [-40, 30]
                    },
                    'properties': {
                        'image-name': 'popup',
                        'name': 'One longer line'
                    }
                }
            ]
        }
    });
    map.addLayer({
        'id': 'points',
        'type': 'symbol',
        'source': 'points',
        'layout': {
            'text-field': ['get', 'name'],
            'icon-text-fit': 'both',
            'icon-image': ['get', 'image-name'],
            'icon-overlap': 'always',
            'text-overlap': 'always'
        }
    });

    // the original, unstretched image for comparison
    map.addSource('original', {
        'type': 'geojson',
        'data': {
            'type': 'FeatureCollection',
            'features': [
                {
                    'type': 'Feature',
                    'geometry': {
                        'type': 'Point',
                        'coordinates': [0, -70]
                    }
                }
            ]
        }
    });
    map.addLayer({
        'id': 'original',
        'type': 'symbol',
        'source': 'original',
        'layout': {
            'text-field': 'unstretched image',
            'icon-image': 'popup-debug',
            'icon-overlap': 'always',
            'text-overlap': 'always'
        }
    });
});

index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="robots" content="noindex">
  <title>Add a stretchable image 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>Add a stretchable image 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, 
        zoom: 0.1
    });

    const images = {
        'popup': 'https://docs.maptiler.com/sdk-js/assets/popup.png',
        'popup-debug':
            'https://docs.maptiler.com/sdk-js/assets/popup_debug.png'
    };

    map.on('load', async () => {
        const debugPopup = await map.loadImage(images['popup-debug']);
        const popup = await map.loadImage(images['popup']);
        map.addImage('popup-debug', debugPopup.data, {
            // The two (blue) columns of pixels that can be stretched horizontally:
            //   - the pixels between x: 25 and x: 55 can be stretched
            //   - the pixels between x: 85 and x: 115 can be stretched.
            stretchX: [
                [25, 55],
                [85, 115]
            ],
            // The one (red) row of pixels that can be stretched vertically:
            //   - the pixels between y: 25 and y: 100 can be stretched
            stretchY: [[25, 100]],
            // This part of the image that can contain text ([x1, y1, x2, y2]):
            content: [25, 25, 115, 100],
            // This is a high-dpi image:
            pixelRatio: 2
        });
        map.addImage('popup', popup.data, {
            stretchX: [
                [25, 55],
                [85, 115]
            ],
            stretchY: [[25, 100]],
            content: [25, 25, 115, 100],
            pixelRatio: 2
        });

        map.addSource('points', {
            'type': 'geojson',
            'data': {
                'type': 'FeatureCollection',
                'features': [
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [40, -30]
                        },
                        'properties': {
                            'image-name': 'popup-debug',
                            'name': 'Line 1\nLine 2\nLine 3'
                        }
                    },
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [40, 30]
                        },
                        'properties': {
                            'image-name': 'popup',
                            'name': 'Line 1\nLine 2\nLine 3'
                        }
                    },
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [-40, -30]
                        },
                        'properties': {
                            'image-name': 'popup-debug',
                            'name': 'One longer line'
                        }
                    },
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [-40, 30]
                        },
                        'properties': {
                            'image-name': 'popup',
                            'name': 'One longer line'
                        }
                    }
                ]
            }
        });
        map.addLayer({
            'id': 'points',
            'type': 'symbol',
            'source': 'points',
            'layout': {
                'text-field': ['get', 'name'],
                'icon-text-fit': 'both',
                'icon-image': ['get', 'image-name'],
                'icon-overlap': 'always',
                'text-overlap': 'always'
            }
        });

        // the original, unstretched image for comparison
        map.addSource('original', {
            'type': 'geojson',
            'data': {
                'type': 'FeatureCollection',
                'features': [
                    {
                        'type': 'Feature',
                        'geometry': {
                            'type': 'Point',
                            'coordinates': [0, -70]
                        }
                    }
                ]
            }
        });
        map.addLayer({
            'id': 'original',
            'type': 'symbol',
            'source': 'original',
            'layout': {
                'text-field': 'unstretched image',
                'icon-image': 'popup-debug',
                'icon-overlap': 'always',
                'text-overlap': 'always'
            }
        });
    });
</script>
</body>
</html>