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 VectorSource from 'ol/source/Vector';
import View from 'ol/View';
import {Fill, Style} from 'ol/style';
import {
Heatmap as HeatmapLayer,
Vector as VectorLayer,
} from 'ol/layer';
import {asArray} from 'ol/color';
const style = new Style({
fill: new Fill({
color: '#eeeeee',
}),
});
const map = new Map({
layers: [
new VectorLayer({
source: new VectorSource({
url: 'https://openlayers.org/data/vector/ecoregions.json',
format: new GeoJSON(),
}),
background: 'white',
style: function (feature) {
const color = asArray(feature.get('COLOR_NNH') || '#eeeeee');
color[3] = 0.75;
style.getFill().setColor(color);
return style;
},
}),
new HeatmapLayer({
source: new VectorSource({
url: 'data/geojson/world-cities.geojson',
format: new GeoJSON(),
}),
weight: function (feature) {
return feature.get('population') / 1e7;
},
radius: 15,
blur: 15,
opacity: 0.75,
}),
],
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(
map.getViewport().querySelectorAll('.ol-layer canvas, canvas.ol-layer'),
function (canvas) {
if (canvas.width > 0) {
const opacity =
canvas.parentNode.style.opacity || canvas.style.opacity;
mapContext.globalAlpha = opacity === '' ? 1 : Number(opacity);
const backgroundColor = canvas.parentNode.style.backgroundColor;
if (backgroundColor) {
mapContext.fillStyle = backgroundColor;
mapContext.fillRect(0, 0, canvas.width, canvas.height);
}
let matrix;
const transform = canvas.style.transform;
if (transform) {
// Get the transform parameters from the style's transform matrix
matrix = transform
.match(/^matrix\(([^\(]*)\)$/)[1]
.split(',')
.map(Number);
} else {
matrix = [
parseFloat(canvas.style.width) / canvas.width,
0,
0,
parseFloat(canvas.style.height) / canvas.height,
0,
0,
];
}
// Apply the transform to the export map context
CanvasRenderingContext2D.prototype.setTransform.apply(
mapContext,
matrix
);
mapContext.drawImage(canvas, 0, 0);
}
}
);
mapContext.globalAlpha = 1;
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/[email protected]/dist/elm-pep.js"></script>
<!-- The lines below are 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,TextDecoder"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/core-js/3.18.3/minified.js"></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": "6.14.1"
},
"devDependencies": {
"parcel": "^2.0.0"
},
"scripts": {
"start": "parcel index.html",
"build": "parcel build --public-url . index.html"
}
}