[Insight-developers] Image Derivatives - physical vs. index space

[Luis Ibanez]

Hi Samuel,

You are right,
the DerivativesImageFilter is not currently taking
the image orientation into account.

It looks like we missed to include this filter in the
list of filters that needed to be adapted.

The itkGradientImageFilter, on the other hand,
was converted to take image orientation into
account.

This was done, first as an option on Oct 2007.
and later converted in to a defauilt on Nov 2008.

See the CVS logs
http://www.itk.org/cgi-bin/viewcvs.cgi/Code/BasicFilters/itkGradientImageFilter.txx?root=Insight&r1=1.21&r2=1.22
http://www.itk.org/cgi-bin/viewcvs.cgi/Code/BasicFilters/itkGradientImageFilter.txx?root=Insight&r1=1.24&r2=1.24.2.1
http://www.itk.org/cgi-bin/viewcvs.cgi/Code/BasicFilters/itkGradientImageFilter.txx?root=Insight&r1=1.24&r2=1.25


Please add a bug entry for the itkDerivativesImageFilter,
in the MANTIS bug tracker:
http://public.kitware.com/Bug/my_view_page.php

The fix will come down to calling the image method:

 inputImage->RotateArrayByDirectionCosines( gradient, rotatedGradient );

after every computation of a derivative vector.



In the meantime,
Could you use the itkGradientImageFilter, instead
of the DerivativesImageFilter for your application ?


      Regards,


            Luis


----------------------------------------------------------------------------------------
On Thu, Jul 2, 2009 at 4:41 PM, Samuel Gerber <sgerber at cs.utah.edu> wrote:

> Hi
>
> I need to compute image derivatives in physical space. From my
> understanding the derivatives computed from itkDerivativesImageFilter are
> either in index space or in physical space but without taking the direction
> into account. I found this page:
> http://www.vtk.org/Wiki/Proposals:Oriented_Image_Registration
> and was wondering what the current status is and the preferred way to
> compute  derivatives in physical space (including orientation).
>
> Thanks
> Sam
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