79c8afdba8
To have the same path (starting with `ol/`, without `.js`) as in the documentation. The support was added in the webpack config in #8928
93 lines
2.6 KiB
JavaScript
93 lines
2.6 KiB
JavaScript
import Map from 'ol/Map';
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import View from 'ol/View';
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import GeoJSON from 'ol/format/GeoJSON';
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import {DEVICE_PIXEL_RATIO} from 'ol/has';
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import VectorLayer from 'ol/layer/Vector';
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import {fromLonLat} from 'ol/proj';
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import VectorSource from 'ol/source/Vector';
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import {Fill, Stroke, Style} from 'ol/style';
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const canvas = document.createElement('canvas');
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const context = canvas.getContext('2d');
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// Gradient and pattern are in canvas pixel space, so we adjust for the
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// renderer's pixel ratio
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const pixelRatio = DEVICE_PIXEL_RATIO;
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// Generate a rainbow gradient
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const gradient = (function() {
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const grad = context.createLinearGradient(0, 0, 512 * pixelRatio, 0);
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grad.addColorStop(0, 'red');
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grad.addColorStop(1 / 6, 'orange');
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grad.addColorStop(2 / 6, 'yellow');
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grad.addColorStop(3 / 6, 'green');
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grad.addColorStop(4 / 6, 'aqua');
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grad.addColorStop(5 / 6, 'blue');
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grad.addColorStop(1, 'purple');
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return grad;
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})();
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// Generate a canvasPattern with two circles on white background
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const pattern = (function() {
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canvas.width = 8 * pixelRatio;
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canvas.height = 8 * pixelRatio;
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// white background
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context.fillStyle = 'white';
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context.fillRect(0, 0, canvas.width, canvas.height);
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// outer circle
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context.fillStyle = 'rgba(102, 0, 102, 0.5)';
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context.beginPath();
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context.arc(4 * pixelRatio, 4 * pixelRatio, 3 * pixelRatio, 0, 2 * Math.PI);
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context.fill();
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// inner circle
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context.fillStyle = 'rgb(55, 0, 170)';
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context.beginPath();
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context.arc(4 * pixelRatio, 4 * pixelRatio, 1.5 * pixelRatio, 0, 2 * Math.PI);
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context.fill();
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return context.createPattern(canvas, 'repeat');
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}());
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// Generate style for gradient or pattern fill
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const fill = new Fill();
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const style = new Style({
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fill: fill,
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stroke: new Stroke({
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color: '#333',
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width: 2
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})
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});
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/**
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* The styling function for the vector layer, will return an array of styles
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* which either contains the aboove gradient or pattern.
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*
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* @param {module:ol/Feature~Feature} feature The feature to style.
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* @return {module:ol/style/Style} The style to use for the feature.
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*/
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const getStackedStyle = function(feature) {
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const id = feature.getId();
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fill.setColor(id > 'J' ? gradient : pattern);
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return style;
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};
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// Create a vector layer that makes use of the style function above…
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const vectorLayer = new VectorLayer({
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source: new VectorSource({
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url: 'data/geojson/countries.geojson',
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format: new GeoJSON()
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}),
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style: getStackedStyle
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});
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// … finally create a map with that layer.
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const map = new Map({
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layers: [
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vectorLayer
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],
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target: 'map',
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view: new View({
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center: fromLonLat([16, 48]),
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zoom: 3
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})
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});
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