[Insight-developers] For your consideration -- enhanced itkWarpImageFilter checked in -- suggestions for further tests?

[Bill Lorensen]

Please stay on top of warnongs and failing PrintSelf test.

Thanks,

Bill

On Wed, Mar 18, 2009 at 12:45 PM, kent williams
<norman-k-williams at uiowa.edu> wrote:
> Thanks to those who helped me do this.  Basically, I put the guts of Tom
> Vercauteren's
> itk::VectorLinearInterpolateNearestNeighborExtrapolateImageFunction into the
> WarpImageFilter.
>
> So now, it finds the deformation at a particular voxel in the output by
> interpolating at that physical point in the deformation field.
>
> Since it uses an interpolator to get values out of the input image, and
> interpolates to find the deformation, the net effect is that the resolutions
> of the input, output, and deformation field are independent -- within
> reason. If they don't cover the same physical area/volume the results will
> be correct but maybe not what you wanted.
>
> I implemented this by comparing the regions of the deformation field and the
> output image. If they're not the same, I interpolate the deformations,
> otherwise the filter behavior is the same as it was before I started
> hacking. It passes the old WarpImageFilter regression test, and a new one I
> wrote. I'll watch for failures on the dashboard, but I think it's pretty
> clean.
>
> Here's my real question: The test I added is pretty simple minded: I warp
> the same image twice, once with a deformation field half the size (with
> twice the spacing) as the output image, and one with a full size deformation
> field.  The deformations are synthetic -- every voxel gets shifted one MM in
> all three directions.
>
> This means that in my test I can create an input image, warp it twice, and
> compare the images in-memory for equivalence.
>
> Any other test I could imagine, the interpolation makes simple-minded
> comparisons of results insufficient because of interpolation.  If someone
> can suggest other tests -- preferably ones that don't involve checking in
> new test data images -- I'd be glad to implement them.
>
>
>
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