Merge pull request #9677 from ahocevar/featureformat-tilepixels

Add support for tile pixel projection in feature formats

examples/geojson-vt.js

@@ -6,7 +6,7 @@ import VectorTileSource from '../src/ol/source/VectorTile.js';
 import {Tile as TileLayer, VectorTile as VectorTileLayer} from '../src/ol/layer.js';
 import Projection from '../src/ol/proj/Projection.js';
 
-
+// Converts geojson-vt data to GeoJSON
 const replacer = function(key, value) {
   if (value.geometry) {
     let type;
@@ -46,11 +46,6 @@ const replacer = function(key, value) {
   }
 };
 
-const tilePixels = new Projection({
-  code: 'TILE_PIXELS',
-  units: 'tile-pixels'
-});
-
 const map = new Map({
   layers: [
     new TileLayer({
@@ -73,23 +68,22 @@ fetch(url).then(function(response) {
     debug: 1
   });
   const vectorSource = new VectorTileSource({
-    format: new GeoJSON(),
-    tileLoadFunction: function(tile) {
-      const format = tile.getFormat();
-      const tileCoord = tile.getTileCoord();
+    format: new GeoJSON({
+      // Data returned from geojson-vt is in tile pixel units
+      dataProjection: new Projection({
+        code: 'TILE_PIXELS',
+        units: 'tile-pixels',
+        extent: [0, 0, 4096, 4096]
+      })
+    }),
+    tileUrlFunction: function(tileCoord) {
       const data = tileIndex.getTile(tileCoord[0], tileCoord[1], tileCoord[2]);
-
-      const features = format.readFeatures(
-        JSON.stringify({
-          type: 'FeatureCollection',
-          features: data ? data.features : []
-        }, replacer));
-      tile.setLoader(function() {
-        tile.setFeatures(features);
-        tile.setProjection(tilePixels);
-      });
-    },
-    url: 'data:' // arbitrary url, we don't use it in the tileLoadFunction
+      const geojson = JSON.stringify({
+        type: 'FeatureCollection',
+        features: data ? data.features : []
+      }, replacer);
+      return 'data:application/json;charset=UTF-8,' + geojson;
+    }
   });
   const vectorLayer = new VectorTileLayer({
     source: vectorSource

src/ol/format/Feature.js

@@ -13,8 +13,10 @@ import {get as getProjection, equivalent as equivalentProjection, transformExten
  * the `dataProjection` of the format is assigned (where set). If the projection
  * can not be derived from the data and if no `dataProjection` is set for a format,
  * the features will not be reprojected.
- * @property {import("../extent.js").Extent} [extent] Tile extent of the tile being read. This is only used and
- * required for {@link module:ol/format/MVT}.
+ * @property {import("../extent.js").Extent} [extent] Tile extent in map units of the tile being read.
+ * This is only required when reading data with tile pixels as geometry units. When configured,
+ * a `dataProjection` with `TILE_PIXELS` as `units` and the tile's pixel extent as `extent` needs to be
+ * provided.
  * @property {import("../proj.js").ProjectionLike} [featureProjection] Projection of the feature geometries
  * created by the format reader. If not provided, features will be returned in the
  * `dataProjection`.
@@ -86,9 +88,14 @@ class FeatureFormat {
   getReadOptions(source, opt_options) {
     let options;
     if (opt_options) {
+      let dataProjection = opt_options.dataProjection ?
+        opt_options.dataProjection : this.readProjection(source);
+      if (opt_options.extent) {
+        dataProjection = getProjection(dataProjection);
+        dataProjection.setWorldExtent(opt_options.extent);
+      }
       options = {
-        dataProjection: opt_options.dataProjection ?
-          opt_options.dataProjection : this.readProjection(source),
+        dataProjection: dataProjection,
         featureProjection: opt_options.featureProjection
       };
     }

test/spec/ol/format/geojson.test.js

@@ -8,7 +8,7 @@ import LinearRing from '../../../../src/ol/geom/LinearRing.js';
 import MultiPolygon from '../../../../src/ol/geom/MultiPolygon.js';
 import Point from '../../../../src/ol/geom/Point.js';
 import Polygon from '../../../../src/ol/geom/Polygon.js';
-import {fromLonLat, get as getProjection, toLonLat, transform} from '../../../../src/ol/proj.js';
+import {fromLonLat, get as getProjection, toLonLat, transform, Projection} from '../../../../src/ol/proj.js';
 
 
 describe('ol.format.GeoJSON', function() {
@@ -260,6 +260,28 @@ describe('ol.format.GeoJSON', function() {
       expect(feature.getGeometry()).to.be.an(Point);
     });
 
+    it('transforms tile pixel coordinates', function() {
+      const geojson = {
+        type: 'Feature',
+        geometry: {
+          type: 'Point',
+          coordinates: [1024, 1024]
+        }
+      };
+      const format = new GeoJSON({
+        dataProjection: new Projection({
+          code: '',
+          units: 'tile-pixels',
+          extent: [0, 0, 4096, 4096]
+        })
+      });
+      const feature = format.readFeature(geojson, {
+        extent: [-180, -90, 180, 90],
+        featureProjection: 'EPSG:3857'
+      });
+      expect(feature.getGeometry().getCoordinates()).to.eql([-135, 45]);
+    });
+
   });
 
   describe('#readFeatures', function() {