[Insight-developers] RecursiveMultiResolutionPyramidImageFilter -- questions about fixing bug 8482

[kent williams]

I don't have an opinion about whether ImageSpacing should be used in these
filters.  I didn't even know what a MultiResolutionPyramidImageFilter was
used for until this morning, when I read the comments in the header.

So to summarize, Tom thinks neither filter should use ImageSpacing for
smoothing. Currently the RecursiveMulti... filter does not, but the
MultiResolution... filter does.

So the choices are 

1. Maintain the status quo (which is inconsistent).
2. Make the two consistently use image spacing (which Tom thinks is wrong in
both cases).
3. Make the two both NOT use image spacing for smoothing (which 'breaks
backward compatibility' w.r.t. the MultiRes...Filter).

I think in the long run choice 3 is the best, if in fact using image spacing
when smoothing is the Wrong Thing To Do.  Failing that, we need to add a
flag on the filter so that the behavior can be turned off for users like
Tom, who don't want it.

On 3/25/09 12:00 PM, "Tom Vercauteren" <tom.vercauteren at gmail.com> wrote:

> Hi Kent,
> 
>> In making RecursiveMultiResolutionPyramidFilter consisitent with
>> MultiResolutionPyramidFilter, I made the smoother use ImageSpacing.  This is
>> consistent; is it desirable?
> 
> Both multi-resolution pyramids define their sigmas in terms of pixel
> sizes, not physical space. Therefore, they should use a smoother with
> UseImageSpacingOff. This is what
> http://public.kitware.com/Bug/view.php?id=503 says.
> 
> I really don't understand why ITK 3.12 introduced UseImageSpacingOn
> instead of UseImageSpacingOff in the smoother of
> MultiResolutionPyramidFilter. This makes no sense to me and broke
> bachwards compatibility.
> 
> A patch should really not introduce this bug also in
> RecursiveMultiResolutionPyramidFilter. I would definitely vote for
> patching MultiResolutionPyramidFilter w.r.t. smoother spacing. This
> will make both pyramids a little more consistent and would fix the bug
> introduced in 3.12. It would not be strictly backwards compatible with
> 3.12 but should be with 3.10 and earlier.
> 
> Let me know if I am missing something.
> 
> Regards,
> Tom



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