[Insight-developers] itk::ImageBase::TransformIndexToPhysicalPoint/TransformPointToContinuousIndex ignores spacing?

[Bill Lorensen]

Look at what I did in ShrinkImageFilter recently. At Hans's request
(do we all work for Hans?) I changed the subsampling so that the image
centers aligned.

Bill

On Tue, Mar 17, 2009 at 11:33 AM, kent williams
<norman-k-williams at uiowa.edu> wrote:
> I was aware of the issue, just never tripped over it before.
>
> I'm just not sure how to deal with it in this case.  It points out a
> fundamental problem in what I'm trying to do.  The net effect is this:
>
> Image A has dimensions { n, n, n } and spacing { s, s, s }
> Image B has dimensions { n/2, n/2, n/2 } and spacing { s*2, s*2, s*2 }
> Assume origin = { 0, 0, 0 } for both, and both are in the same orientation.
>
> Any physical point on an edge farthest from the origin -- e.g. { n-1, y, z
> }, { x, n-1, z }, { x, y, n-1 } etc -- is INSIDE image A, but NOT INSIDE
> image B.  Even though the two images theoretically have the same volume.
>
> And this is independent of whether the index is center-of-voxel or corner of
> voxel, or whether you're a North-going Zax or a South-going Zax.
>
> The mind reels.
>
> On 3/17/09 1:01 PM, "Tom Vercauteren" <tom.vercauteren at gmail.com> wrote:
>
>> Hi Kent,
>>
>> You might already be aware of that bug:
>> http://www.itk.org/Bug/view.php?id=6558
>>
>> Right now the use of rounding vs. truncation is not consistent within
>> the index <-> world transformations.
>>
>> Tom
>>
>
>
>
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