The `OGRGeometry.coord_dim` property may now be set; implemented a work-around for an OGR bug that changed geometries to 3D after transformation. Refs #11433.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11628 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/gdal/geometries.py

@@ -179,10 +179,17 @@ class OGRGeometry(GDALBase):
         "Returns 0 for points, 1 for lines, and 2 for surfaces."
         return capi.get_dims(self.ptr)
 
-    @property
+    def _get_coord_dim(self):
-    def coord_dim(self):
         "Returns the coordinate dimension of the Geometry."
-        return capi.get_coord_dims(self.ptr)
+        return capi.get_coord_dim(self.ptr)
+
+    def _set_coord_dim(self, dim):
+        "Sets the coordinate dimension of this Geometry."
+        if not dim in (2, 3):
+            raise ValueError('Geometry dimension must be either 2 or 3')
+        capi.set_coord_dim(self.ptr, dim)
+
+    coord_dim = property(_get_coord_dim, _set_coord_dim)
 
     @property
     def geom_count(self):
@@ -363,6 +370,16 @@ class OGRGeometry(GDALBase):
             klone = self.clone()
             klone.transform(coord_trans)
             return klone
+
+        # Have to get the coordinate dimension of the original geometry
+        # so it can be used to reset the transformed geometry's dimension
+        # afterwards.  This is done because of GDAL bug (in versions prior
+        # to 1.7) that turns geometries 3D after transformation, see:
+        #  http://trac.osgeo.org/gdal/changeset/17792
+        orig_dim = self.coord_dim
+
+        # Depending on the input type, use the appropriate OGR routine
+        # to perform the transformation.
         if isinstance(coord_trans, CoordTransform):
             capi.geom_transform(self.ptr, coord_trans.ptr)
         elif isinstance(coord_trans, SpatialReference):
@@ -373,6 +390,10 @@ class OGRGeometry(GDALBase):
         else:
             raise TypeError('Transform only accepts CoordTransform, SpatialReference, string, and integer objects.')
 
+        # Setting with original dimension, see comment above.
+        if self.coord_dim != orig_dim:
+            self.coord_dim = orig_dim
+
     def transform_to(self, srs):
         "For backwards-compatibility."
         self.transform(srs)

django/contrib/gis/gdal/prototypes/geom.py

@@ -83,7 +83,8 @@ get_geom_srs = srs_output(lgdal.OGR_G_GetSpatialReference, [c_void_p])
 get_area = double_output(lgdal.OGR_G_GetArea, [c_void_p])
 get_centroid = void_output(lgdal.OGR_G_Centroid, [c_void_p, c_void_p])
 get_dims = int_output(lgdal.OGR_G_GetDimension, [c_void_p])
-get_coord_dims = int_output(lgdal.OGR_G_GetCoordinateDimension, [c_void_p])
+get_coord_dim = int_output(lgdal.OGR_G_GetCoordinateDimension, [c_void_p])
+set_coord_dim = void_output(lgdal.OGR_G_SetCoordinateDimension, [c_void_p, c_int], errcheck=False)
 
 get_geom_count = int_output(lgdal.OGR_G_GetGeometryCount, [c_void_p])
 get_geom_name = const_string_output(lgdal.OGR_G_GetGeometryName, [c_void_p])

django/contrib/gis/gdal/tests/test_geom.py

@@ -319,6 +319,18 @@ class OGRGeomTest(unittest.TestCase):
             self.assertAlmostEqual(trans.x, p.x, prec)
             self.assertAlmostEqual(trans.y, p.y, prec)
 
+    def test09c_transform_dim(self):
+        "Testing coordinate dimension is the same on transformed geometries."
+        ls_orig = OGRGeometry('LINESTRING(-104.609 38.255)', 4326)
+        ls_trans = OGRGeometry('LINESTRING(992385.4472045 481455.4944650)', 2774)
+        
+        prec = 3
+        ls_orig.transform(ls_trans.srs)
+        # Making sure the coordinate dimension is still 2D.
+        self.assertEqual(2, ls_orig.coord_dim)
+        self.assertAlmostEqual(ls_trans.x[0], ls_orig.x[0], prec)
+        self.assertAlmostEqual(ls_trans.y[0], ls_orig.y[0], prec)
+
     def test10_difference(self):
         "Testing difference()."
         for i in xrange(len(topology_geoms)):