Update canvas gradient example

examples/canvas-gradient-pattern.html

@@ -1,13 +1,11 @@
 ---
 layout: example.html
 title: Styling feature with CanvasGradient or CanvasPattern
-shortdesc: Example showing the countries vector layer styled with patterns and gradients.
+shortdesc: Example showing a vector layer styled with a gradient.
 docs: >
-  This example creates a [`CanvasPattern`](https://developer.mozilla.org/en-US/docs/Web/API/CanvasPattern)
-  and a [`CanvasGradient`](https://developer.mozilla.org/en/docs/Web/API/CanvasGradient). The countries are loaded from
-  a GeoJSON file. A style function determines for each country whether to use a fill with the
-  CanvasGradient (rainbow colors) or a CanvasPattern (repeating stacked circles). **Note**: For seamless repeat patterns,
-  image width and height of the pattern image must be a factor of two (2, 4, 8, ..., 512).
+  This example creates a [`CanvasGradient`](https://developer.mozilla.org/en/docs/Web/API/CanvasGradient).
+  The vector data is loaded from a file and features are filled with the gradient.
+  The same technique can be used with a [`CanvasPattern`](https://developer.mozilla.org/en-US/docs/Web/API/CanvasPattern).
 tags: "canvas, gradient, pattern, style"
 ---
 <div id="map" class="map"></div>

examples/canvas-gradient-pattern.js

@@ -1,4 +1,4 @@
-import GeoJSON from '../src/ol/format/GeoJSON.js';
+import KML from '../src/ol/format/KML.js';
 import Map from '../src/ol/Map.js';
 import VectorLayer from '../src/ol/layer/Vector.js';
 import VectorSource from '../src/ol/source/Vector.js';
@@ -7,84 +7,42 @@ import {DEVICE_PIXEL_RATIO} from '../src/ol/has.js';
 import {Fill, Stroke, Style} from '../src/ol/style.js';
 import {fromLonLat} from '../src/ol/proj.js';
 
-const canvas = document.createElement('canvas');
-const context = canvas.getContext('2d');
-
 // Gradient and pattern are in canvas pixel space, so we adjust for the
 // renderer's pixel ratio
 const pixelRatio = DEVICE_PIXEL_RATIO;
 
 // Generate a rainbow gradient
-const gradient = (function () {
-  const grad = context.createLinearGradient(0, 0, 512 * pixelRatio, 0);
-  grad.addColorStop(0, 'red');
-  grad.addColorStop(1 / 6, 'orange');
-  grad.addColorStop(2 / 6, 'yellow');
-  grad.addColorStop(3 / 6, 'green');
-  grad.addColorStop(4 / 6, 'aqua');
-  grad.addColorStop(5 / 6, 'blue');
-  grad.addColorStop(1, 'purple');
-  return grad;
-})();
+const canvas = document.createElement('canvas');
+const context = canvas.getContext('2d');
+const gradient = context.createLinearGradient(0, 0, 1024 * pixelRatio, 0);
+gradient.addColorStop(0, 'red');
+gradient.addColorStop(1 / 6, 'orange');
+gradient.addColorStop(2 / 6, 'yellow');
+gradient.addColorStop(3 / 6, 'green');
+gradient.addColorStop(4 / 6, 'aqua');
+gradient.addColorStop(5 / 6, 'blue');
+gradient.addColorStop(1, 'purple');
 
-// Generate a canvasPattern with two circles on white background
-const pattern = (function () {
-  canvas.width = 8 * pixelRatio;
-  canvas.height = 8 * pixelRatio;
-  // white background
-  context.fillStyle = 'white';
-  context.fillRect(0, 0, canvas.width, canvas.height);
-  // outer circle
-  context.fillStyle = 'rgba(102, 0, 102, 0.5)';
-  context.beginPath();
-  context.arc(4 * pixelRatio, 4 * pixelRatio, 3 * pixelRatio, 0, 2 * Math.PI);
-  context.fill();
-  // inner circle
-  context.fillStyle = 'rgb(55, 0, 170)';
-  context.beginPath();
-  context.arc(4 * pixelRatio, 4 * pixelRatio, 1.5 * pixelRatio, 0, 2 * Math.PI);
-  context.fill();
-  return context.createPattern(canvas, 'repeat');
-})();
-
-// Generate style for gradient or pattern fill
-const fill = new Fill();
-const style = new Style({
-  fill: fill,
+const vectorLayer = new VectorLayer({
+  background: 'white',
+  source: new VectorSource({
+    url: 'data/kml/states.kml',
+    format: new KML({extractStyles: false}),
+  }),
+  style: new Style({
+    fill: new Fill({color: gradient}),
     stroke: new Stroke({
       color: '#333',
-    width: 2,
+      width: 1,
+    }),
   }),
 });
 
-/**
- * The styling function for the vector layer, will return an array of styles
- * which either contains the aboove gradient or pattern.
- *
- * @param {import("../src/ol/Feature.js").default} feature The feature to style.
- * @return {Style} The style to use for the feature.
- */
-const getStackedStyle = function (feature) {
-  const id = feature.getId();
-  fill.setColor(id > 'J' ? gradient : pattern);
-  return style;
-};
-
-// Create a vector layer that makes use of the style function above…
-const vectorLayer = new VectorLayer({
-  source: new VectorSource({
-    url: 'data/geojson/countries.geojson',
-    format: new GeoJSON(),
-  }),
-  style: getStackedStyle,
-});
-
-// … finally create a map with that layer.
 const map = new Map({
   layers: [vectorLayer],
   target: 'map',
   view: new View({
-    center: fromLonLat([16, 48]),
-    zoom: 3,
+    center: fromLonLat([-100, 38.5]),
+    zoom: 4,
   }),
 });