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

[Tom Vercauteren]

Kent,

You might also want to switch the interpolator for an
interpolator/extrapolator such as the one I contributed to the Review
directory:
http://www.itk.org/Doxygen/html/classitk_1_1VectorLinearInterpolateNearestNeighborExtrapolateImageFunction.html

With this function, all points are considered as inside the buffer. I
think that this approach makes sense in your case.

Hope this helps,
Tom

On Tue, Mar 17, 2009 at 19:43, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> 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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>