[Insight-users] itk::VectorResampleImageFilter

[Lars Friedrich]

Hello itk-users,

I have a little question regarding itk::VectorResampleImageFilter:

I use the vector resample image filter for initial rigid transformations 
of various 3D deformation fields (PixelType = itk::Vector<float, 3>) 
which are later used for generating an instance of an appearance model 
through warping. The VectorResampleImageFilter transforms the vectors, 
but the direction of the vectors (voxels) is not changed (I tried to 
depict this with some ASCII-arts below ;)) because the components of the 
vectors are simply interpolated for the new transformed position and 
copied. In my case I need the change of the vector-direction (according 
to the applied transformation) too. Because otherwise the warping later 
generates 'irregular' model instances.


original (showing the problem in 2D where the slashes should illustrate 
a vector - direction to the right upper corner):

|--------------------------------|
|                                |
|         /                      |
|        /                       |
|                                |
O--------------------------------|



applied transformation: +90 degrees around the deformation field's 
origin (O)


this is what itk::VectorResampleImageFilter does (the direction is not 
changed):

-----------
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|      /  |
|     /   |
|         |
|         |
|         |
O----------


desirable in my case (vector is now pointing to the left upper corner):

-----------
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|         |
|    \    |
|     \   |
|         |
|         |
|         |
O----------


So, my question is: is there a simple way to achieve the change of 
vector direction too in ITK or do I have to modify and implement 
itk::VectorResampleImageFilter?

I would be very very grateful for an answer!!

regards,
Lars