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.