Add ol.geom.flat.flipXY

src/ol/geom/flatgeom.js

@@ -74,6 +74,40 @@ ol.geom.flat.deflateCoordinatesss =
 };
 
 
+/**
+ * @param {Array.<number>} flatCoordinates Flat coordinates.
+ * @param {number} offset Offset.
+ * @param {number} end End.
+ * @param {number} stride Stride.
+ * @param {Array.<number>=} opt_dest Destination.
+ * @param {number=} opt_destOffset Destination offset.
+ * @return {Array.<number>} Flat coordinates.
+ */
+ol.geom.flat.flipXY =
+    function(flatCoordinates, offset, end, stride, opt_dest, opt_destOffset) {
+  var dest, destOffset;
+  if (goog.isDef(opt_dest)) {
+    dest = opt_dest;
+    destOffset = goog.isDef(opt_destOffset) ? opt_destOffset : 0;
+  } else {
+    goog.asserts.assert(!goog.isDef(opt_destOffset));
+    dest = [];
+    destOffset = 0;
+  }
+  var j, k;
+  for (j = offset; j < end; ) {
+    var x = flatCoordinates[j++];
+    dest[destOffset++] = flatCoordinates[j++];
+    dest[destOffset++] = x;
+    for (k = 2; k < stride; ++k) {
+      dest[destOffset++] = flatCoordinates[j++];
+    }
+  }
+  dest.length = destOffset;
+  return dest;
+};
+
+
 /**
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {number} offset Offset.

test/spec/ol/geom/flatgeom.test.js

@@ -44,6 +44,37 @@ describe('ol.geom.flat', function() {
 
   });
 
+  describe('ol.geom.flat.flipXY', function() {
+
+    it('can flip XY coordinates', function() {
+      var flatCoordinates = ol.geom.flat.flipXY([1, 2, 3, 4], 0, 4, 2);
+      expect(flatCoordinates).to.eql([2, 1, 4, 3]);
+    });
+
+    it('can flip XY coordinates while preserving other dimensions', function() {
+      var flatCoordinates = ol.geom.flat.flipXY(
+          [1, 2, 3, 4, 5, 6, 7, 8], 0, 8, 4);
+      expect(flatCoordinates).to.eql([2, 1, 3, 4, 6, 5, 7, 8]);
+    });
+
+    it('can flip XY coordinates in place', function() {
+      var flatCoordinates = [1, 2, 3, 4];
+      expect(ol.geom.flat.flipXY(flatCoordinates, 0, 4, 2, flatCoordinates)).
+          to.be(flatCoordinates);
+      expect(flatCoordinates).to.eql([2, 1, 4, 3]);
+    });
+
+    it('can flip XY coordinates in place while preserving other dimensions',
+        function() {
+          var flatCoordinates = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+          expect(ol.geom.flat.flipXY(
+              flatCoordinates, 0, 9, 3, flatCoordinates)).
+              to.be(flatCoordinates);
+          expect(flatCoordinates).to.eql([2, 1, 3, 5, 4, 6, 8, 7, 9]);
+        });
+
+  });
+
   describe('ol.geom.flat.inflateCoordinatess', function() {
 
     it('inflates arrays of coordinates', function() {