OpenLayers
OpenLayers
Example of exporting a map as a PNG image.
Example of exporting a map as a PNG image.
import Map from 'ol/Map.js';
import View from 'ol/View.js';
import {asArray} from 'ol/color.js';
import GeoJSON from 'ol/format/GeoJSON.js';
import HeatmapLayer from 'ol/layer/Heatmap.js';
import VectorLayer from 'ol/layer/Vector.js';
import VectorSource from 'ol/source/Vector.js';
import Fill from 'ol/style/Fill.js';
import Style from 'ol/style/Style.js';
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);
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,
);
const backgroundColor = canvas.parentNode.style.backgroundColor;
if (backgroundColor) {
mapContext.fillStyle = backgroundColor;
mapContext.fillRect(0, 0, canvas.width, canvas.height);
}
mapContext.drawImage(canvas, 0, 0);
}
},
);
mapContext.globalAlpha = 1;
mapContext.setTransform(1, 0, 0, 1, 0, 0);
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>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@fortawesome/[email protected]/css/fontawesome.min.css">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@fortawesome/[email protected]/css/solid.css">
<link rel="stylesheet" href="node_modules/ol/ol.css">
<style>
.map {
width: 100%;
height: 400px;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<a id="export-png" class="btn btn-outline-dark" role="button"><i class="fa fa-download"></i> Download PNG</a>
<a id="image-download" download="map.png"></a>
<script type="module" src="main.js"></script>
</body>
</html>{
"name": "export-map",
"dependencies": {
"ol": "10.6.1"
},
"devDependencies": {
"vite": "^3.2.3"
},
"scripts": {
"start": "vite",
"build": "vite build"
}
}