[Insight-users] itk::Image vs. itk::OrientedImage

[Luis Ibanez]

Daniel,

If you are using the CVS HEAD version of ITK,
you can also turn ON the following CMake flag:


     ITK_IMAGE_BEHAVES_AS_ORIENTED_IMAGE


This will make the itk::Image behavior to be the
same as the itk::OrientedImage.


You will have to go to the "Advanced" variables
in CMake, to see this flag.


This option will be available in the upcoming
release of ITK 3.10.


    Regards,


        Luis


-------------------
Daniel Betz wrote:
> Hello,
> 
> I have an itk::Image with orientation like this:
> 
> origin:[-125, -124.1, 79.3]
> spacing:[0.9375, 0.9375, 3]
> direction:
> 1 0 0
> 0 1 0
> 0 0 -1
> 
> Now I take a valid pixel index:
> 
> Pixel Index: [134, 112, 11]
> 
> and ask with itk::Image::TransformIndexToPhysicalPoint() for the coordinates
> in physical space and get:
> 
> Physical Point: [0.625, -19.1, 112.3]
> 
> This is not a physical point inside my image, because the direction of the
> z-axis is negativ. So the z-component 112.3 is outside of my image, because
> the image starts at origin 79.3 (z-axis).
> 
> Reading the source code I determined, that 
> itk::Image::TransformIndexToPhysicalPoint()
> does not take direction into account.
> 
> But there is the class itk::OrientedImage which handles the orientation
> correctly.
> 
> My question is, why is SetDirection() in itk::Image available, since the
> Transform Methods will not use it anyway. Why has itk::Image only a
> "fake orientation" and why I need itk::OrientedImage for a
> "real orientation" ?
> The design decission to handle it that way is not visible for
> me.
> 
> In the Doxygen documentation of itk::Image is written, that some functions are
> implemented differently in itk::OrientedImage. I think that is not enough and
> it should be documented more explicitly that I can set the direction in an 
> itk::Image even though it will not taken into account by the transform 
> methods.
> 
> Sincerly
> Daniel Betz
> 
> 
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