ENH: add support for direction in VTK image

Wrapping/Generators/Python/Tests/extras.py

@@ -586,6 +586,10 @@ def custom_callback(name, progress):
 
     print("Testing vtk conversion")
     image = itk.image_from_array(np.random.rand(2, 3, 4))
+    z_rot = np.asarray([[0,1,0], [-1,0,0], [0,0,1]], dtype=np.float64)
+    z_rot_itk = itk.matrix_from_array(z_rot)
+    image.SetDirection(z_rot_itk)
+
     vtk_image = itk.vtk_image_from_image(image)
     image_round = itk.image_from_vtk_image(vtk_image)
     assert np.array_equal(itk.origin(image), itk.origin(image_round))
@@ -594,10 +598,20 @@ def custom_callback(name, progress):
     assert np.array_equal(
         itk.array_view_from_image(image), itk.array_view_from_image(image_round)
     )
+    if vtk.vtkVersion.GetVTKMajorVersion()>=9:
+        z_rot_round = itk.array_from_matrix(image_round.GetDirection())
+        assert np.array_equal(z_rot, z_rot_round)
+    else:
+        print("VTK version <9. Direction unsupported.")
+
 
     image = itk.image_from_array(
         np.random.rand(5, 4, 2).astype(np.float32), is_vector=True
     )
+    z_rot = np.asarray([[0,1], [-1,0]], dtype=np.float64)
+    z_rot_itk = itk.matrix_from_array(z_rot)
+    image.SetDirection(z_rot_itk)
+
     vtk_image = itk.vtk_image_from_image(image)
     image_round = itk.image_from_vtk_image(vtk_image)
     assert np.array_equal(itk.origin(image), itk.origin(image_round))
@@ -606,6 +620,10 @@ def custom_callback(name, progress):
     assert np.array_equal(
         itk.array_view_from_image(image), itk.array_view_from_image(image_round)
     )
+    if vtk.vtkVersion.GetVTKMajorVersion()>=9:
+        z_rot_round = itk.array_from_matrix(image_round.GetDirection())
+        assert np.array_equal(z_rot, z_rot_round)
+
 except ImportError:
     print("vtk not imported. Skipping vtk conversion tests")
     pass

Wrapping/Generators/Python/itk/support/extras.py

@@ -731,7 +731,17 @@ def vtk_image_from_image(l_image: "itkt.ImageOrImageSource") -> "vtk.vtkImageDat
     dims = [1] * 3
     dims[:dim] = itk.size(l_image)
     vtk_image.SetDimensions(dims)
-    # Todo: Add Direction with VTK 9
+    # Copy direction matrix for VTK>=9
+    import vtk
+    if vtk.vtkVersion.GetVTKMajorVersion()>=9:
+        l_direction = l_image.GetDirection()
+        direction = itk.array_from_matrix(l_direction).flatten().tolist()
+        if len(direction) == 4:
+            # Change 2d matrix to 3d
+            direction = [ direction[0], direction[1], 0.0,
+                          direction[2], direction[3], 0.0,
+                                   0.0,          0.0, 1.0 ]
+        vtk_image.SetDirectionMatrix(direction)
     if l_image.GetImageDimension() == 3:
         PixelType = itk.template(l_image)[1][0]
         if PixelType == itk.Vector:
@@ -772,7 +782,22 @@ def image_from_vtk_image(vtk_image: "vtk.vtkImageData") -> "itkt.ImageBase":
     l_origin = [0.0] * dim
     l_origin[:dim] = vtk_image.GetOrigin()[:dim]
     l_image.SetOrigin(l_origin)
-    # Todo: Add Direction with VTK 9
+    # Direction support with VTK 9
+    import vtk
+    if vtk.vtkVersion.GetVTKMajorVersion()>=9:
+        direction = vtk_image.GetDirectionMatrix()
+        if dim==3:
+            direction_array = np.identity(3)
+            for y in (0,1,2):
+                for x in (0,1,2):
+                    direction_array[x,y] = direction.GetElement(x,y)
+        elif dim==2:
+            direction_array = np.identity(2)
+            for y in (0,1):
+                for x in (0,1):
+                    direction_array[x,y] = direction.GetElement(x,y)
+        l_direction = itk.matrix_from_array(direction_array)
+        l_image.SetDirection(l_direction)
     return l_image