103 lines
3.3 KiB
JavaScript
103 lines
3.3 KiB
JavaScript
import Map from '../src/ol/Map.js';
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import View from '../src/ol/View.js';
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import {getWidth} from '../src/ol/extent.js';
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import GeoJSON from '../src/ol/format/GeoJSON.js';
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import {DEVICE_PIXEL_RATIO} from '../src/ol/has.js';
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import VectorLayer from '../src/ol/layer/Vector.js';
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import {fromLonLat} from '../src/ol/proj.js';
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import VectorSource from '../src/ol/source/Vector.js';
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import Fill from '../src/ol/style/Fill.js';
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import Stroke from '../src/ol/style/Stroke.js';
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import Style from '../src/ol/style/Style.js';
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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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function gradient(feature, resolution) {
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const extent = feature.getGeometry().getExtent();
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// Gradient starts on the left edge of each feature, and ends on the right.
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// Coordinate origin is the top-left corner of the extent of the geometry, so
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// we just divide the geometry's extent width by resolution and multiply with
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// pixelRatio to match the renderer's pixel coordinate system.
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const grad = context.createLinearGradient(0, 0,
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getWidth(extent) / resolution * 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 = 11 * pixelRatio;
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canvas.height = 11 * 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(5 * pixelRatio, 5 * pixelRatio, 4 * 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(5 * pixelRatio, 5 * pixelRatio, 2 * 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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* @param {number} resolution Resolution.
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* @return {ol.style.Style} The style to use for the feature.
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*/
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const getStackedStyle = function(feature, resolution) {
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const id = feature.getId();
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fill.setColor(id > 'J' ? gradient(feature, resolution) : 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([7, 52]),
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zoom: 3
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})
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});
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