Allow orienting coordinates when serializing GeoJSON

externs/olx.js

@@ -1538,7 +1538,8 @@ olx.format;
 
 /**
  * @typedef {{dataProjection: ol.proj.ProjectionLike,
- *     featureProjection: ol.proj.ProjectionLike}}
+ *     featureProjection: ol.proj.ProjectionLike,
+ *     rightHanded: (boolean|undefined)}}
  * @api
  */
 olx.format.ReadOptions;
@@ -1567,7 +1568,8 @@ olx.format.ReadOptions.prototype.featureProjection;
 
 /**
  * @typedef {{dataProjection: ol.proj.ProjectionLike,
- *     featureProjection: ol.proj.ProjectionLike}}
+ *     featureProjection: ol.proj.ProjectionLike,
+ *     rightHanded: (boolean|undefined)}}
  * @api
  */
 olx.format.WriteOptions;
@@ -1593,6 +1595,22 @@ olx.format.WriteOptions.prototype.dataProjection;
 olx.format.WriteOptions.prototype.featureProjection;
 
 
+/**
+ * When writing geometries, follow the right-hand rule for linear ring
+ * orientation.  This means that polygons will have counter-clockwise exterior
+ * rings and clockwise interior rings.  By default, coordinates are serialized
+ * as they are provided at construction.  If `true`, the right-hand rule will
+ * be applied.  If `false`, the left-hand rule will be applied (clockwise for
+ * exterior and counter-clockwise for interior rings).  Note that not all
+ * formats support this.  The GeoJSON format does use this property when writing
+ * geometries.
+ *
+ * @type {boolean|undefined}
+ * @api
+ */
+olx.format.WriteOptions.prototype.rightHanded;
+
+
 /**
  * @typedef {{defaultDataProjection: ol.proj.ProjectionLike,
  *     geometryName: (string|undefined)}}

src/ol/format/featureformat.js

@@ -68,7 +68,8 @@ ol.format.Feature.prototype.adaptOptions = function(options) {
     updatedOptions = {
       featureProjection: options.featureProjection,
       dataProjection: goog.isDefAndNotNull(options.dataProjection) ?
-          options.dataProjection : this.defaultDataProjection
+          options.dataProjection : this.defaultDataProjection,
+      rightHanded: options.rightHanded
     };
   }
   return updatedOptions;

src/ol/format/geojsonformat.js

@@ -178,7 +178,8 @@ ol.format.GeoJSON.writeGeometry_ = function(geometry, opt_options) {
   var geometryWriter = ol.format.GeoJSON.GEOMETRY_WRITERS_[geometry.getType()];
   goog.asserts.assert(goog.isDef(geometryWriter));
   return geometryWriter(/** @type {ol.geom.Geometry} */ (
-      ol.format.Feature.transformWithOptions(geometry, true, opt_options)));
+      ol.format.Feature.transformWithOptions(geometry, true, opt_options)),
+      opt_options);
 };
 
 
@@ -217,10 +218,11 @@ ol.format.GeoJSON.writeGeometryCollectionGeometry_ = function(
 
 /**
  * @param {ol.geom.Geometry} geometry Geometry.
+ * @param {olx.format.WriteOptions=} opt_options Write options.
  * @private
  * @return {GeoJSONGeometry} GeoJSON geometry.
  */
-ol.format.GeoJSON.writeLineStringGeometry_ = function(geometry) {
+ol.format.GeoJSON.writeLineStringGeometry_ = function(geometry, opt_options) {
   goog.asserts.assertInstanceof(geometry, ol.geom.LineString);
   return /** @type {GeoJSONGeometry} */ ({
     'type': 'LineString',
@@ -231,10 +233,12 @@ ol.format.GeoJSON.writeLineStringGeometry_ = function(geometry) {
 
 /**
  * @param {ol.geom.Geometry} geometry Geometry.
+ * @param {olx.format.WriteOptions=} opt_options Write options.
  * @private
  * @return {GeoJSONGeometry} GeoJSON geometry.
  */
-ol.format.GeoJSON.writeMultiLineStringGeometry_ = function(geometry) {
+ol.format.GeoJSON.writeMultiLineStringGeometry_ =
+    function(geometry, opt_options) {
   goog.asserts.assertInstanceof(geometry, ol.geom.MultiLineString);
   goog.asserts.assert(
       geometry.getType() == ol.geom.GeometryType.MULTI_LINE_STRING);
@@ -247,10 +251,11 @@ ol.format.GeoJSON.writeMultiLineStringGeometry_ = function(geometry) {
 
 /**
  * @param {ol.geom.Geometry} geometry Geometry.
+ * @param {olx.format.WriteOptions=} opt_options Write options.
  * @private
  * @return {GeoJSONGeometry} GeoJSON geometry.
  */
-ol.format.GeoJSON.writeMultiPointGeometry_ = function(geometry) {
+ol.format.GeoJSON.writeMultiPointGeometry_ = function(geometry, opt_options) {
   goog.asserts.assertInstanceof(geometry, ol.geom.MultiPoint);
   return /** @type {GeoJSONGeometry} */ ({
     'type': 'MultiPoint',
@@ -261,24 +266,30 @@ ol.format.GeoJSON.writeMultiPointGeometry_ = function(geometry) {
 
 /**
  * @param {ol.geom.Geometry} geometry Geometry.
+ * @param {olx.format.WriteOptions=} opt_options Write options.
  * @private
  * @return {GeoJSONGeometry} GeoJSON geometry.
  */
-ol.format.GeoJSON.writeMultiPolygonGeometry_ = function(geometry) {
+ol.format.GeoJSON.writeMultiPolygonGeometry_ = function(geometry, opt_options) {
   goog.asserts.assertInstanceof(geometry, ol.geom.MultiPolygon);
+  var right;
+  if (goog.isDef(opt_options)) {
+    right = opt_options.rightHanded;
+  }
   return /** @type {GeoJSONGeometry} */ ({
     'type': 'MultiPolygon',
-    'coordinates': geometry.getCoordinates()
+    'coordinates': geometry.getCoordinates(right)
   });
 };
 
 
 /**
  * @param {ol.geom.Geometry} geometry Geometry.
+ * @param {olx.format.WriteOptions=} opt_options Write options.
  * @private
  * @return {GeoJSONGeometry} GeoJSON geometry.
  */
-ol.format.GeoJSON.writePointGeometry_ = function(geometry) {
+ol.format.GeoJSON.writePointGeometry_ = function(geometry, opt_options) {
   goog.asserts.assertInstanceof(geometry, ol.geom.Point);
   return /** @type {GeoJSONGeometry} */ ({
     'type': 'Point',
@@ -289,14 +300,19 @@ ol.format.GeoJSON.writePointGeometry_ = function(geometry) {
 
 /**
  * @param {ol.geom.Geometry} geometry Geometry.
+ * @param {olx.format.WriteOptions=} opt_options Write options.
  * @private
  * @return {GeoJSONGeometry} GeoJSON geometry.
  */
-ol.format.GeoJSON.writePolygonGeometry_ = function(geometry) {
+ol.format.GeoJSON.writePolygonGeometry_ = function(geometry, opt_options) {
   goog.asserts.assertInstanceof(geometry, ol.geom.Polygon);
+  var right;
+  if (goog.isDef(opt_options)) {
+    right = opt_options.rightHanded;
+  }
   return /** @type {GeoJSONGeometry} */ ({
     'type': 'Polygon',
-    'coordinates': geometry.getCoordinates()
+    'coordinates': geometry.getCoordinates(right)
   });
 };
 
@@ -320,7 +336,7 @@ ol.format.GeoJSON.GEOMETRY_READERS_ = {
 /**
  * @const
  * @private
- * @type {Object.<string, function(ol.geom.Geometry): (GeoJSONGeometry|GeoJSONGeometryCollection)>}
+ * @type {Object.<string, function(ol.geom.Geometry, olx.format.WriteOptions=): (GeoJSONGeometry|GeoJSONGeometryCollection)>}
  */
 ol.format.GeoJSON.GEOMETRY_WRITERS_ = {
   'Point': ol.format.GeoJSON.writePointGeometry_,

test/spec/ol/format/geojsonformat.test.js

@@ -558,6 +558,106 @@ describe('ol.format.GeoJSON', function() {
           format.readGeometry(geojson).getCoordinates());
     });
 
+    it('maintains coordinate order by default', function() {
+
+      var cw = [[-180, -90], [-180, 90], [180, 90], [180, -90], [-180, -90]];
+      var ccw = [[-180, -90], [180, -90], [180, 90], [-180, 90], [-180, -90]];
+
+      var right = new ol.geom.Polygon([ccw, cw]);
+      var rightMulti = new ol.geom.MultiPolygon([[ccw, cw]]);
+      var left = new ol.geom.Polygon([cw, ccw]);
+      var leftMulti = new ol.geom.MultiPolygon([[cw, ccw]]);
+
+      var rightObj = {
+        type: 'Polygon',
+        coordinates: [ccw, cw]
+      };
+
+      var rightMultiObj = {
+        type: 'MultiPolygon',
+        coordinates: [[ccw, cw]]
+      };
+
+      var leftObj = {
+        type: 'Polygon',
+        coordinates: [cw, ccw]
+      };
+
+      var leftMultiObj = {
+        type: 'MultiPolygon',
+        coordinates: [[cw, ccw]]
+      };
+
+      expect(JSON.parse(format.writeGeometry(right))).to.eql(rightObj);
+      expect(
+          JSON.parse(format.writeGeometry(rightMulti))).to.eql(rightMultiObj);
+      expect(JSON.parse(format.writeGeometry(left))).to.eql(leftObj);
+      expect(JSON.parse(format.writeGeometry(leftMulti))).to.eql(leftMultiObj);
+
+    });
+
+    it('allows serializing following the right-hand rule', function() {
+
+      var cw = [[-180, -90], [-180, 90], [180, 90], [180, -90], [-180, -90]];
+      var ccw = [[-180, -90], [180, -90], [180, 90], [-180, 90], [-180, -90]];
+      var right = new ol.geom.Polygon([ccw, cw]);
+      var rightMulti = new ol.geom.MultiPolygon([[ccw, cw]]);
+      var left = new ol.geom.Polygon([cw, ccw]);
+      var leftMulti = new ol.geom.MultiPolygon([[cw, ccw]]);
+
+      var rightObj = {
+        type: 'Polygon',
+        coordinates: [ccw, cw]
+      };
+
+      var rightMultiObj = {
+        type: 'MultiPolygon',
+        coordinates: [[ccw, cw]]
+      };
+
+      var json = format.writeGeometry(right, {rightHanded: true});
+      expect(JSON.parse(json)).to.eql(rightObj);
+      json = format.writeGeometry(rightMulti, {rightHanded: true});
+      expect(JSON.parse(json)).to.eql(rightMultiObj);
+
+      json = format.writeGeometry(left, {rightHanded: true});
+      expect(JSON.parse(json)).to.eql(rightObj);
+      json = format.writeGeometry(leftMulti, {rightHanded: true});
+      expect(JSON.parse(json)).to.eql(rightMultiObj);
+
+    });
+
+    it('allows serializing following the left-hand rule', function() {
+
+      var cw = [[-180, -90], [-180, 90], [180, 90], [180, -90], [-180, -90]];
+      var ccw = [[-180, -90], [180, -90], [180, 90], [-180, 90], [-180, -90]];
+      var right = new ol.geom.Polygon([ccw, cw]);
+      var rightMulti = new ol.geom.MultiPolygon([[ccw, cw]]);
+      var left = new ol.geom.Polygon([cw, ccw]);
+      var leftMulti = new ol.geom.MultiPolygon([[cw, ccw]]);
+
+      var leftObj = {
+        type: 'Polygon',
+        coordinates: [cw, ccw]
+      };
+
+      var leftMultiObj = {
+        type: 'MultiPolygon',
+        coordinates: [[cw, ccw]]
+      };
+
+      var json = format.writeGeometry(right, {rightHanded: false});
+      expect(JSON.parse(json)).to.eql(leftObj);
+      json = format.writeGeometry(rightMulti, {rightHanded: false});
+      expect(JSON.parse(json)).to.eql(leftMultiObj);
+
+      json = format.writeGeometry(left, {rightHanded: false});
+      expect(JSON.parse(json)).to.eql(leftObj);
+      json = format.writeGeometry(leftMulti, {rightHanded: false});
+      expect(JSON.parse(json)).to.eql(leftMultiObj);
+
+    });
+
     it('encodes geometry collection', function() {
       var collection = new ol.geom.GeometryCollection([
         new ol.geom.Point([10, 20]),
@@ -611,6 +711,7 @@ goog.require('ol.geom.Circle');
 goog.require('ol.geom.GeometryCollection');
 goog.require('ol.geom.LineString');
 goog.require('ol.geom.LinearRing');
+goog.require('ol.geom.MultiPolygon');
 goog.require('ol.geom.Point');
 goog.require('ol.geom.Polygon');
 goog.require('ol.proj');