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

[Bill Lorensen]

Kent,

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Bill

On Wed, Mar 18, 2009 at 4:25 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> 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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>