Add new ol.geom.Geometry#rotate function

src/ol/geom/flat/transformflatgeom.js

@@ -35,6 +35,39 @@ ol.geom.flat.transform.transform2D = function(flatCoordinates, offset, end, stri
 };
 
 
+/**
+ * @param {Array.<number>} flatCoordinates Flat coordinates.
+ * @param {number} offset Offset.
+ * @param {number} end End.
+ * @param {number} stride Stride.
+ * @param {number} angle Angle.
+ * @param {Array.<number>} anchor Rotation anchor point.
+ * @param {Array.<number>=} opt_dest Destination.
+ * @return {Array.<number>} Transformed coordinates.
+ */
+ol.geom.flat.transform.rotate = function(flatCoordinates, offset, end, stride, angle, anchor, opt_dest) {
+  var dest = opt_dest ? opt_dest : [];
+  var cos = Math.cos(angle);
+  var sin = Math.sin(angle);
+  var anchorX = anchor[0];
+  var anchorY = anchor[1];
+  var i = 0;
+  for (var j = offset; j < end; j += stride) {
+    var deltaX = flatCoordinates[j] - anchorX;
+    var deltaY = flatCoordinates[j + 1] - anchorY;
+    dest[i++] = anchorX + deltaX * cos - deltaY * sin;
+    dest[i++] = anchorY + deltaX * sin + deltaY * cos;
+    for (var k = j + 2; k < j + stride; ++k) {
+      dest[i++] = flatCoordinates[k];
+    }
+  }
+  if (opt_dest && dest.length != i) {
+    dest.length = i;
+  }
+  return dest;
+};
+
+
 /**
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {number} offset Offset.

src/ol/geom/geometry.js

@@ -169,6 +169,16 @@ ol.geom.Geometry.prototype.getExtent = function(opt_extent) {
 };
 
 
+/**
+ * Rotate the geometry around a given coordinate. This modifies the geometry
+ * coordinates in place.
+ * @param {number} angle Rotation angle in radians.
+ * @param {ol.Coordinate} anchor The rotation center.
+ * @api
+ */
+ol.geom.Geometry.prototype.rotate = goog.abstractMethod;
+
+
 /**
  * Create a simplified version of this geometry.  For linestrings, this uses
  * the the {@link

src/ol/geom/geometrycollection.js

@@ -231,6 +231,19 @@ ol.geom.GeometryCollection.prototype.isEmpty = function() {
 };
 
 
+/**
+ * @inheritDoc
+ * @api
+ */
+ol.geom.GeometryCollection.prototype.rotate = function(angle, anchor) {
+  var geometries = this.geometries_;
+  for (var i = 0, ii = geometries.length; i < ii; ++i) {
+    geometries[i].rotate(angle, anchor);
+  }
+  this.changed();
+};
+
+
 /**
  * Set the geometries that make up this geometry collection.
  * @param {Array.<ol.geom.Geometry>} geometries Geometries.

src/ol/geom/simplegeometry.js

@@ -260,6 +260,22 @@ ol.geom.SimpleGeometry.prototype.applyTransform = function(transformFn) {
 };
 
 
+/**
+ * @inheritDoc
+ * @api
+ */
+ol.geom.SimpleGeometry.prototype.rotate = function(angle, anchor) {
+  var flatCoordinates = this.getFlatCoordinates();
+  if (flatCoordinates) {
+    var stride = this.getStride();
+    ol.geom.flat.transform.rotate(
+        flatCoordinates, 0, flatCoordinates.length,
+        stride, angle, anchor, flatCoordinates);
+    this.changed();
+  }
+};
+
+
 /**
  * @inheritDoc
  * @api stable

test/spec/ol/geom/flat/transformflatgeom.test.js

@@ -79,6 +79,51 @@ describe('ol.geom.flat.transform', function() {
     });
   });
 
+  describe('ol.geom.flat.transform.rotate', function() {
+    it('rotates the coordinates array', function() {
+      var multiPolygon = new ol.geom.MultiPolygon([
+        [[[0, 0, 2], [0, 1, 2], [1, 1, 2], [1, 0, 2], [0, 0, 2]]],
+        [[[2, 2, 3], [2, 3, 3], [3, 3, 3], [3, 2, 3], [2, 2, 3]]]]);
+      var flatCoordinates = multiPolygon.getFlatCoordinates();
+      var angle = Math.PI / 2;
+      var anchor = [0, 1];
+      ol.geom.flat.transform.rotate(flatCoordinates, 0,
+          flatCoordinates.length, multiPolygon.getStride(),
+          angle, anchor, flatCoordinates);
+      expect(flatCoordinates[0]).to.roughlyEqual(1, 1e-9);
+      expect(flatCoordinates[1]).to.roughlyEqual(1, 1e-9);
+      expect(flatCoordinates[2]).to.roughlyEqual(2, 1e-9);
+      expect(flatCoordinates[3]).to.roughlyEqual(0, 1e-9);
+      expect(flatCoordinates[4]).to.roughlyEqual(1, 1e-9);
+      expect(flatCoordinates[5]).to.roughlyEqual(2, 1e-9);
+      expect(flatCoordinates[6]).to.roughlyEqual(Math.cos(angle), 1e-9);
+      expect(flatCoordinates[7]).to.roughlyEqual(2, 1e-9);
+      expect(flatCoordinates[8]).to.roughlyEqual(2, 1e-9);
+      expect(flatCoordinates[9]).to.roughlyEqual(1, 1e-9);
+      expect(flatCoordinates[10]).to.roughlyEqual(2, 1e-9);
+      expect(flatCoordinates[11]).to.roughlyEqual(2, 1e-9);
+      expect(flatCoordinates[12]).to.roughlyEqual(1, 1e-9);
+      expect(flatCoordinates[13]).to.roughlyEqual(1, 1e-9);
+      expect(flatCoordinates[14]).to.roughlyEqual(2, 1e-9);
+      expect(flatCoordinates[15]).to.roughlyEqual(-1, 1e-9);
+      expect(flatCoordinates[16]).to.roughlyEqual(3, 1e-9);
+      expect(flatCoordinates[17]).to.roughlyEqual(3, 1e-9);
+      expect(flatCoordinates[18]).to.roughlyEqual(-2, 1e-9);
+      expect(flatCoordinates[19]).to.roughlyEqual(3, 1e-9);
+      expect(flatCoordinates[20]).to.roughlyEqual(3, 1e-9);
+      expect(flatCoordinates[21]).to.roughlyEqual(-2, 1e-9);
+      expect(flatCoordinates[22]).to.roughlyEqual(4, 1e-9);
+      expect(flatCoordinates[23]).to.roughlyEqual(3, 1e-9);
+      expect(flatCoordinates[24]).to.roughlyEqual(-1, 1e-9);
+      expect(flatCoordinates[25]).to.roughlyEqual(4, 1e-9);
+      expect(flatCoordinates[26]).to.roughlyEqual(3, 1e-9);
+      expect(flatCoordinates[27]).to.roughlyEqual(-1, 1e-9);
+      expect(flatCoordinates[28]).to.roughlyEqual(3, 1e-9);
+      expect(flatCoordinates[29]).to.roughlyEqual(3, 1e-9);
+    });
+
+  });
+
 });
 
 goog.require('ol.geom.MultiPolygon');