60 lines
1.6 KiB
JavaScript
60 lines
1.6 KiB
JavaScript
import GeoJSON from '../src/ol/format/GeoJSON.js';
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import Map from '../src/ol/Map.js';
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import View from '../src/ol/View.js';
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import {Fill, Style} from '../src/ol/style.js';
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import {OSM, Stamen, Vector as VectorSource} from '../src/ol/source.js';
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import {Tile as TileLayer, Vector as VectorLayer} from '../src/ol/layer.js';
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import {fromLonLat} from '../src/ol/proj.js';
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import {getVectorContext} from '../src/ol/render.js';
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import {intersects} from '../src/ol/extent.js';
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//A distinct className is required to use another canvas for the background
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const background = new TileLayer({
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className: 'stamen',
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source: new Stamen({
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layer: 'toner',
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}),
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});
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const base = new TileLayer({
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source: new OSM(),
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});
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const clipLayer = new VectorLayer({
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style: null,
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source: new VectorSource({
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url: './data/geojson/switzerland.geojson',
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format: new GeoJSON(),
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}),
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});
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const style = new Style({
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fill: new Fill({
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color: 'black',
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}),
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});
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base.on('postrender', function (e) {
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const vectorContext = getVectorContext(e);
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e.context.globalCompositeOperation = 'destination-in';
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//Checking interect is required so the base layer is totally hidden when not clipped
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if (intersects(e.frameState.extent, clipLayer.getSource().getExtent())) {
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clipLayer.getSource().forEachFeature(function (feature) {
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vectorContext.drawFeature(feature, style);
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});
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} else {
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e.context.fillStyle = 'transparent';
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e.context.fillRect(0, 0, 1, 1);
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}
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e.context.globalCompositeOperation = 'source-over';
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});
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const map = new Map({
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layers: [background, base, clipLayer],
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target: 'map',
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view: new View({
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center: fromLonLat([8.23, 46.86]),
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zoom: 7,
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}),
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});
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