[Insight-developers] ImageSpatialObject Bug0006340

[Bill Lorensen]

Rupert,

In general, itkImage directions are ignored (assumed identity).
itkOrientedImage directions are used. I have not looked at the
ImageSpatialObject yet. If it uses Transform{X}To{Y} type calls, then
Image and OrientedImage should behave properly. I don't think itkImage
should behave differently inside and outside of itkImageSpatialObject.

Bill

On Tue, Aug 5, 2008 at 1:58 PM, Rupert Brooks <rupe.brooks at gmail.com> wrote:
> Hi Everyone,
>
> As Luis wisely suggested i waited until after the 3.8 release to work
> on this  :-)  I still need some big picture advice thoug
>> Please note that the first action to take, even before experimenting
>> with a fix, is to add a tests that illustrates the failure. E.g. to
>> add a test that exercise the condition you have identified as
>> problematic.
>
> I've added the test (itkImageMaskSpatialObjectTest2), and you all
> should notice it failing in your dashboards shortly :-)
>
> Theres more than one way to patch the problem - i'll refer back to my
> previous email.  I think theres a conceptual bug, or at least
> confusion in the itk::Image. I cant decide how i should make
> ImageSpatialObject behave when handed an ITK image that has
> non-identity directions.
>
>>> Briefly, the image spatial object takes the coordinate transform from
>>> the image that it is given, and uses that as its IndexToWorld
>>> transformation.  Previously, it was ignoring the direction.  The fix
>>> was a matter of adding the necessary lines to copy the direction
>>> information also.
>>>
>>> However, this fix raises a further issue, and I'd like advice:
>>>
>>> The itk::Image class may have a non-identity direction component, but
>>> it always ignores it.  However, a naive implementation of my fix would
>>> use that direction information, giving a different behavior than the
>>> itk::Image.  I could write code to check if its an ITK image, and then
>>> behave differently, but this seems inelegant at best.   Is this
>>> actually another bug - should an itk::Image always have an identity
>>> direction, to conform with its behavior?  Can i ignore the issue,
>>> assuming the user will be bright enough to only put direction
>>> information in an itk::Image for a very good reason.
>
> Does anyone have some insights into how the itkImageSpatialObject
> should behave when handed an itk::Image which has non-identity
> direction cosines?
>
> (the bug in question is this one
> http://public.kitware.com/Bug/view.php?id=0006340)
>
> Cheers
> Rupert B.
>
>
> --
> --------------------------------------------------------------
> Rupert Brooks
> McGill Centre for Intelligent Machines (www.cim.mcgill.ca)
> Ph.D Student, Electrical and Computer Engineering
> http://www.cyberus.ca/~rbrooks
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