Example of exporting a map as a PNG image.
Example of exporting a map as a PNG image.
import 'ol/ol.css';
import GeoJSON from 'ol/format/GeoJSON';
import Map from 'ol/Map';
import View from 'ol/View';
import {OSM, Vector as VectorSource} from 'ol/source';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
const map = new Map({
layers: [
new TileLayer({
source: new OSM(),
}),
new VectorLayer({
source: new VectorSource({
url: 'data/geojson/countries.geojson',
format: new GeoJSON(),
}),
opacity: 0.5,
}),
],
target: 'map',
view: new View({
center: [0, 0],
zoom: 2,
}),
});
document.getElementById('export-png').addEventListener('click', function () {
map.once('rendercomplete', function () {
const mapCanvas = document.createElement('canvas');
const size = map.getSize();
mapCanvas.width = size[0];
mapCanvas.height = size[1];
const mapContext = mapCanvas.getContext('2d');
Array.prototype.forEach.call(
document.querySelectorAll('.ol-layer canvas'),
function (canvas) {
if (canvas.width > 0) {
const opacity = canvas.parentNode.style.opacity;
mapContext.globalAlpha = opacity === '' ? 1 : Number(opacity);
const transform = canvas.style.transform;
// Get the transform parameters from the style's transform matrix
const matrix = transform
.match(/^matrix\(([^\(]*)\)$/)[1]
.split(',')
.map(Number);
// Apply the transform to the export map context
CanvasRenderingContext2D.prototype.setTransform.apply(
mapContext,
matrix
);
mapContext.drawImage(canvas, 0, 0);
}
}
);
if (navigator.msSaveBlob) {
// link download attribute does not work on MS browsers
navigator.msSaveBlob(mapCanvas.msToBlob(), 'map.png');
} else {
const link = document.getElementById('image-download');
link.href = mapCanvas.toDataURL();
link.click();
}
});
map.renderSync();
});
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Map Export</title>
<!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
<script src="https://unpkg.com/elm-pep"></script>
<!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
<script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL,TextDecoder,Number.isInteger"></script>
<style>
.map {
width: 100%;
height:400px;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<a id="export-png" class="btn btn-default"><i class="fa fa-download"></i> Download PNG</a>
<a id="image-download" download="map.png"></a>
<script src="main.js"></script>
</body>
</html>
{
"name": "export-map",
"dependencies": {
"ol": "6.6.1"
},
"devDependencies": {
"parcel": "^2.0.0-beta.1"
},
"scripts": {
"start": "parcel index.html",
"build": "parcel build --public-url . index.html"
}
}