Merge pull request #6381 from drnextgis/geojson-vt

geojson-vt integration example

examples/.eslintrc

@@ -5,12 +5,13 @@
     "common": false,
     "createMapboxStreetsV6Style": false,
     "d3": false,
+    "geojsonvt": false,
     "jsPDF": false,
     "jsts": false,
-    "topolis": false,
-    "toastr": false,
     "saveAs": false,
+    "toastr": false,
     "topojson": false,
+    "topolis": false,
     "turf": false
   },
   "rules": {

examples/geojson-vt.html

@@ -0,0 +1,11 @@
+---
+layout: example.html
+title: geojson-vt integration
+shortdesc: Slice GeoJSON into vector tiles on the fly in the browser.
+docs: >
+  Example of integration with <a href="https://github.com/mapbox/geojson-vt">geojson-vt</a> library.
+tags: "mapbox, vector, tiles, geojson"
+resources:
+  - https://mapbox.github.io/geojson-vt/geojson-vt-dev.js
+---
+<div id="map" class="map"></div>

examples/geojson-vt.js

@@ -0,0 +1,91 @@
+// NOCOMPILE
+goog.require('ol.Map');
+goog.require('ol.View');
+goog.require('ol.format.GeoJSON');
+goog.require('ol.source.OSM');
+goog.require('ol.source.VectorTile');
+goog.require('ol.layer.Tile');
+goog.require('ol.layer.VectorTile');
+goog.require('ol.tilegrid');
+goog.require('ol.proj');
+
+
+var replacer = function(key, value) {
+  if (value.geometry) {
+    var type;
+    var rawType = value.type;
+    var geometry = value.geometry;
+
+    if (rawType === 1) {
+      type = geometry.length === 1 ? 'Point' : 'MultiPoint';
+    } else if (rawType === 2) {
+      type = geometry.length === 1 ? 'LineString' : 'MultiLineString';
+    } else if (rawType === 3) {
+      type = geometry.length === 1 ? 'Polygon' : 'MultiPolygon';
+    }
+
+    return {
+      'type': 'Feature',
+      'geometry': {
+        'type': type,
+        'coordinates': geometry.length == 1 ? geometry : [geometry]
+      },
+      'properties': value.tags
+    };
+  } else {
+    return value;
+  }
+};
+
+var tilePixels = new ol.proj.Projection({
+  code: 'TILE_PIXELS',
+  units: 'tile-pixels'
+});
+
+var map = new ol.Map({
+  layers: [
+    new ol.layer.Tile({
+      source: new ol.source.OSM()
+    })
+  ],
+  target: 'map',
+  view: new ol.View({
+    center: [0, 0],
+    zoom: 2
+  })
+});
+
+var url = 'data/geojson/countries.geojson';
+fetch(url).then(function(response) {
+  return response.json();
+}).then(function(json) {
+  var tileIndex = geojsonvt(json, {
+    extent: 4096,
+    debug: 1
+  });
+  var vectorSource = new ol.source.VectorTile({
+    format: new ol.format.GeoJSON(),
+    tileGrid: ol.tilegrid.createXYZ(),
+    tilePixelRatio: 16,
+    tileLoadFunction: function(tile) {
+      var format = tile.getFormat();
+      var tileCoord = tile.getTileCoord();
+      var data = tileIndex.getTile(tileCoord[0], tileCoord[1], -tileCoord[2] - 1);
+
+      var 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
+  });
+  var vectorLayer = new ol.layer.VectorTile({
+    source: vectorSource
+  });
+  map.addLayer(vectorLayer);
+});