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Align patterns and gradients to a grid

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This commit is contained in:
ahocevar
2018-05-22 16:05:32 +02:00
parent c32bd2274c
commit 7cfa65b8c3
6 changed files with 24 additions and 25 deletions
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28
examples/canvas-gradient-pattern.js
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@@ -1,6 +1,5 @@
import Map from '../src/ol/Map.js';
import View from '../src/ol/View.js';
import {getWidth} from '../src/ol/extent.js';
import GeoJSON from '../src/ol/format/GeoJSON.js';
import {DEVICE_PIXEL_RATIO} from '../src/ol/has.js';
import VectorLayer from '../src/ol/layer/Vector.js';
@@ -16,14 +15,8 @@ const context = canvas.getContext('2d');
const pixelRatio = DEVICE_PIXEL_RATIO;
// Generate a rainbow gradient
function gradient(feature, resolution) {
const extent = feature.getGeometry().getExtent();
// Gradient starts on the left edge of each feature, and ends on the right.
// Coordinate origin is the top-left corner of the extent of the geometry, so
// we just divide the geometry's extent width by resolution and multiply with
// pixelRatio to match the renderer's pixel coordinate system.
const grad = context.createLinearGradient(0, 0,
getWidth(extent) / resolution * pixelRatio, 0);
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');
@@ -32,24 +25,24 @@ function gradient(feature, resolution) {
grad.addColorStop(5 / 6, 'blue');
grad.addColorStop(1, 'purple');
return grad;
}
})();
// Generate a canvasPattern with two circles on white background
const pattern = (function() {
canvas.width = 11 * pixelRatio;
canvas.height = 11 * pixelRatio;
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(5 * pixelRatio, 5 * pixelRatio, 4 * pixelRatio, 0, 2 * Math.PI);
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(5 * pixelRatio, 5 * pixelRatio, 2 * pixelRatio, 0, 2 * Math.PI);
context.arc(4 * pixelRatio, 4 * pixelRatio, 1.5 * pixelRatio, 0, 2 * Math.PI);
context.fill();
return context.createPattern(canvas, 'repeat');
}());
@@ -69,12 +62,11 @@ const style = new Style({
* which either contains the aboove gradient or pattern.
*
* @param {module:ol/Feature~Feature} feature The feature to style.
* @param {number} resolution Resolution.
* @return {module:ol/style/Style} The style to use for the feature.
*/
const getStackedStyle = function(feature, resolution) {
const getStackedStyle = function(feature) {
const id = feature.getId();
fill.setColor(id > 'J' ? gradient(feature, resolution) : pattern);
fill.setColor(id > 'J' ? gradient : pattern);
return style;
};
@@ -94,7 +86,7 @@ const map = new Map({
],
target: 'map',
view: new View({
center: fromLonLat([7, 52]),
center: fromLonLat([16, 48]),
zoom: 3
})
});