[Insight-developers] Should Filters propogate theDirection Cosines from Image input to image output?

[Miller, James V (Research)]

I think that line is coping the direction vectors from the reference
image not the input image.  Specifying a reference image is optional.
If specied, then the output gets the spacing, origin, and directions
from that image instead of having to specify them individually via
method calls.

Jim

-----Original Message-----
From: insight-developers-bounces+millerjv=crd.ge.com at itk.org
[mailto:insight-developers-bounces+millerjv=crd.ge.com at itk.org]On Behalf
Of Luis Ibanez
Sent: Tuesday, November 01, 2005 1:05 PM
To: Lorensen, William E (Research)
Cc: Insight-developers (E-mail); Kent Williams
Subject: Re: [Insight-developers] Should Filters propogate theDirection
Cosines from Image input to image output?



Isn't that what lines 299 and 305 do in

    Insight/Code/BasicFilters/itkResampleImageFilter.txx:


299:  outputPtr->SetDirection( m_ReferenceImage->GetDirection() );


Jim: The direction cosines should be passed as they are, not being
affected by the transform itself, since, if we transform the pixels
*and* the direction cosines we will end up applying a null transform
or a double transform.



    Luis



----------------------------------------
Lorensen, William E (Research) wrote:
> Yes they should. I'm surprised ResampleImageFilter does not propagate them. I thought I did that already.
> 
> Bill
> 
> -----Original Message-----
> From: insight-developers-bounces+lorensen=crd.ge.com at itk.org
> [mailto:insight-developers-bounces+lorensen=crd.ge.com at itk.org]On Behalf
> Of Kent Williams
> Sent: Monday, October 31, 2005 2:34 PM
> To: Insight-developers (E-mail)
> Subject: [Insight-developers] Should Filters propogate the Direction
> Cosines from Image input to image output?
> 
> 
> I discovered this when using ResampleImageFilter to shrink some image 
> volumes -- the ResampleImageFilter doesn't propogate the Direction 
> Cosines from the input image into the output image. Consequently if you 
> write out the resulting image it may not be oriented consistent with the 
> input image.
> 
> Should filters set the Direction Cosines on the output? I know that 
> itk::OrientImageFilter does so, which is natural since it is changing 
> the orientation. But what about filters like ResampleImageFilter, which 
> does not change the image orientation?  What about the cases where an 
> output image is produced from more than one input image?
> 
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