[Insight-users] Combining 3 images

Luis Ibanez luis.ibanez at kitware.com
Tue May 24 11:31:35 EDT 2005



Hi Vera,



The filter that you need is the


itkCompose3DVectorImageFilter
http://www.itk.org/Insight/Doxygen/html/classitk_1_1Compose3DVectorImageFilter.html


and/or the


itkCompose3DCovariantVectorImageFilter
http://www.itk.org/Insight/Doxygen/html/classitk_1_1Compose3DCovariantVectorImageFilter.html



Note that ITK differentiates between "Vectors" which are defined
as the difference between two positions in space, and "CovariantVectors"
which are defined as the orthogonal direction to a (N-1)-dimensional
subspace.  Covariant vectors represent Gradients, and Normals to
Surfaces (in 3D), while "Vectors" represent the relative position
between two points.


This distinction is quite important when you apply AffineTransforms
to this geometrical objects.



Now that... from your email, you seems to be dealing with Second
Derivatives, in which case you are dealing with a symmetric Tensor
of Second Rank with two Covariant components. In that context you
should be careful since this object does  not behave as a Vector,
nor a CovariantVector.  In case you need it, we recently add a
Second rank symmetric tensor class to ITK.



Please let us know if you have any further questions,



     Thanks




       Luis



----------------------
Vera Naumburger wrote:

> Hi,
> 
> I´m trying to combine three gradient images (xy, yz, zx), so that the  
> output is a VectorImage. I found the JoinImageFilter for
> joining 2 images, is there something like that for 3 images, as well?
> 
> Thanks,
> Vera
> _______________________________________________
> Insight-users mailing list
> Insight-users at itk.org
> http://www.itk.org/mailman/listinfo/insight-users
> 
> 





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