[ITK-dev] image and deformation field physical space check

[M.Staring at lumc.nl]

Hi all,

Would it be possible to fix this issue by passing the physical space by reference, or by performing an exact copy?

Regards, Marius

> -----Original Message-----
> From: Insight-developers [mailto:insight-developers-bounces at itk.org] On
> Behalf Of Matt McCormick
> Sent: maandag 3 november 2014 18:39
> To: brian avants
> Cc: Insight-developers at itk.org
> Subject: Re: [ITK-dev] image and deformation field physical space check
> 
> Hi Brian,
> 
> Thanks for discussing this.
> 
> I think a combination of fixing the underlying issue that is being brought up by
> the exception, relaxing the tolerance, and improving the documentation is a
> good approach.
> 
> 2 cents,
> Matt
> 
> On Mon, Nov 3, 2014 at 11:40 AM, brian avants <stnava at gmail.com> wrote:
> > This email is motivated by this issue:
> >
> > https://github.com/stnava/ANTs/issues/74
> >
> > but it is not isolated to ants.   Worth a read for additional context.
> >
> > ITK currently enforces a relatively strict check that image and
> > displacement fields "occupy the same physical space."  However, for
> > some unclear (to me) reasons, the direction matrices or origins of
> > images can lose precision when passing through ITK pipelines (
> > especially through resampling or resolution-changing filters ).  This
> > results in filters aborting and this can occur at various different
> > places in a complex series of ITK-based operations.
> >
> > My concern with this is that it can lead to a very severe loss of
> > productivity when this somewhat unpredictable error occurs.   For instance,
> > a user downloads a toolkit based on ITK ( itk-snap, ants, elastic,
> > brainsfit, joint label fusion, etc).   The user expects registration or
> > segmentation filters to "work well" especially when the data is of a
> > standard sort.   Then, after some oft-substantial execution time, this
> > mysterious error appears:
> >
> > itk::ERROR: ImageToImageFilter(0x7fb3b2307ac0): Inputs do not occupy
> > the same physical space!
> >
> >
> > While I am all for correctness, when the impact on productivity exceeds a
> > certain threshold, I think it is useful to bend the rules a bit.   Perhaps
> > one of these would improve the situation:
> >
> > 1)    change:
> >
> > ITKv4/Modules/Filtering/DisplacementField/include/itkDisplacementField
> > Transform.hxx
> >
> > and
> >
> > ITKv4/Modules/Core/Common/include/itkImageToImageFilter.hxx
> >
> > changing direction tolerance and coordinate tolerance to 1.e-4
> >
> > https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/F
> > iltering/DisplacementField/include/itkDisplacementFieldTransform.hxx#L
> > 454-L457
> >
> > https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/C
> > ore/Common/include/itkImageToImageFilter.hxx#L40-L41
> >
> > and change the documentation too:
> >
> > https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/C
> > ore/Common/include/itkImageToImageFilter.h#L76-L87
> >
> > 2)  Change the exception to a warning.  This would at least allow
> > complex pipelines to execute while notifying the user of a possible issue.
> >
> > 3)  Document all of the places that the user/developer should call:
> >
> > Set/GetCoordinateTolerance  Set/GetDirectionTolerance  .
> >
> > This last solution would require adding Set/GetCoordinate and
> > Direction tolerance to:
> >
> > https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/F
> > iltering/DisplacementField/include/itkDisplacementFieldTransform.h
> >
> > as well, for consistency.
> >
> > Anyway, I raise this issue b/c of the many man and computer hours lost
> > by this check.
> >
> > Not once has this check actually helped us, in any measurable way,
> > avoid errors.
> >
> >
> >
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