Example of using OpenLayers and d3 together.
The example loads TopoJSON geometries and uses d3 (d3.geo.path
) to render these geometries to a SVG element.
import Map from 'ol/Map.js';
import StadiaMaps from 'ol/source/StadiaMaps.js';
import View from 'ol/View.js';
import {Layer, Tile as TileLayer} from 'ol/layer.js';
import {feature} from 'topojson-client';
import {fromLonLat, toLonLat} from 'ol/proj.js';
import {geoBounds, geoMercator, geoPath} from 'd3-geo';
import {getCenter, getWidth} from 'ol/extent.js';
import {json} from 'd3-fetch';
import {select} from 'd3-selection';
class CanvasLayer extends Layer {
constructor(options) {
super(options);
this.features = options.features;
this.svg = select(document.createElement('div'))
.append('svg')
.style('position', 'absolute');
this.svg.append('path').datum(this.features).attr('class', 'boundary');
}
getSourceState() {
return 'ready';
}
render(frameState) {
const width = frameState.size[0];
const height = frameState.size[1];
const projection = frameState.viewState.projection;
const d3Projection = geoMercator().scale(1).translate([0, 0]);
let d3Path = geoPath().projection(d3Projection);
const pixelBounds = d3Path.bounds(this.features);
const pixelBoundsWidth = pixelBounds[1][0] - pixelBounds[0][0];
const pixelBoundsHeight = pixelBounds[1][1] - pixelBounds[0][1];
const bounds = geoBounds(this.features);
const geoBoundsLeftBottom = fromLonLat(bounds[0], projection);
const geoBoundsRightTop = fromLonLat(bounds[1], projection);
let geoBoundsWidth = geoBoundsRightTop[0] - geoBoundsLeftBottom[0];
if (geoBoundsWidth < 0) {
geoBoundsWidth += getWidth(projection.getExtent());
}
const geoBoundsHeight = geoBoundsRightTop[1] - geoBoundsLeftBottom[1];
const widthResolution = geoBoundsWidth / pixelBoundsWidth;
const heightResolution = geoBoundsHeight / pixelBoundsHeight;
const r = Math.max(widthResolution, heightResolution);
const scale = r / frameState.viewState.resolution;
const center = toLonLat(getCenter(frameState.extent), projection);
const angle = (-frameState.viewState.rotation * 180) / Math.PI;
d3Projection
.scale(scale)
.center(center)
.translate([width / 2, height / 2])
.angle(angle);
d3Path = d3Path.projection(d3Projection);
d3Path(this.features);
this.svg.attr('width', width);
this.svg.attr('height', height);
this.svg.select('path').attr('d', d3Path);
return this.svg.node();
}
}
const map = new Map({
layers: [
new TileLayer({
source: new StadiaMaps({
layer: 'stamen_watercolor',
}),
}),
],
target: 'map',
view: new View({
center: fromLonLat([-97, 38]),
zoom: 4,
}),
});
/**
* Load the topojson data and create an ol/layer/Layer for that data.
*/
json('data/topojson/us.json').then(function (us) {
const layer = new CanvasLayer({
features: feature(us, us.objects.counties),
});
map.addLayer(layer);
});
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>d3 Integration</title>
<link rel="stylesheet" href="node_modules/ol/ol.css">
<style>
.map {
width: 100%;
height: 400px;
}
path.boundary {
fill: none;
stroke: #777;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<script type="module" src="main.js"></script>
</body>
</html>
{
"name": "d3",
"dependencies": {
"ol": "10.3.1",
"topojson-client": "^3.1.0",
"d3-geo": "^3.1.1",
"d3-fetch": "^3.0.1",
"d3-selection": "^3.0.0"
},
"devDependencies": {
"vite": "^3.2.3"
},
"scripts": {
"start": "vite",
"build": "vite build"
}
}