[Insight-developers] So -- no concensus on smoothing re MultiResolutionPyramidImageFilter?

[Stephen Aylward]

I could be misunderstanding...but shouldn't the default be "true" to
keep backward compatibility?

Having an option to offer backward compatibility, but having the
default be to not enable backward compatibility seems very odd (ok, it
seems simply wrong).

Bill?

Luis?

Stephen

On Thu, Apr 9, 2009 at 7:30 AM, Hans Johnson <hans-johnson at uiowa.edu> wrote:
> Since this is considered a bug for over a year
> http://www.vtk.org/Bug/view.php?id=7002 we should consider the fact that
> MultiResolutionPyramidImageFilter smooths for unit shrink factors a bug that
> would allow us to fix it (even through numerical sameness/backwards
> compatibility will be lost).
>
> This is not the behavior that I would expect by reading the documentation on
> how an Image Pyramid should be constructed (i.e. The top level should be an
> exact copy of the reference images).
>
> I think that this is a bug that also affects the
> RecursiveMultiResolutionPyramidImageFilter because it would produce
> different results for the unit shrink factor image if I change the shrink
> schedule from being downward divisible to being non-downward divisible.
> This is particularly nasty because given the same "shrink schedule
> [8,4,2,1]" the unit shrink result will be different depending on the size of
> the input image.
>
> ===============
> If there are no objects today, then the solution that will be implemented
> will be:
>
> 1) Add a test that fails when the unit shrink image is not the same as the
> reference image (and the m_SmoothIfUnitShrinkFactors =false).
> 2) Add the m_SmoothIfUnitShrinkFactors conditional flag to allow explicit
> smoothing of the unit shrink factors.
> 3) Set the default to "false" in all cases.
> ===============
>
>
> Regards,
> Hans
>
>
> On 4/9/09 1:56 AM, "Tom Vercauteren" <tom.vercauteren at gmail.com> wrote:
>
>> Hi Kent,
>>
>> Even if there is no consensus about what the default should be, it
>> could be add a flag that lets the user decide (as Stephen suggested).
>>
>> Maybe something like:
>>   m_SmoothIfUnitShrinkFactors
>>
>> For backwards compatibility, the default for this flag would be:
>>   - true for MultiResolutionPyramidImageFilter
>>   - false for RecursiveMultiResolutionPyramidImageFilter
>>
>> Now, I also would like to propose a NON-backward compatible change to
>> fix something that might be very confusing to the user.
>>
>> Since RecursiveMultiResolutionPyramidImageFilter wil call
>> MultiResolutionPyramidImageFilter if the schedule is not downward
>> divisible, I suggest that RecursiveMultiResolutionPyramidImageFilter
>> sets
>>
>> internalNonRecursivePyramid->SetSmoothIfUnitShrinkFactors(this->m_SmoothIfUnit
>> ShrinkFactors)
>> when the schedule is not downward divisible.
>>
>> With this small non-backward compatible change, it would at least make
>> things a bit clearer.
>>
>> Otherwise we might need a three state flag for
>> RecursiveMultiResolutionPyramidImageFilter:
>>   - AlwaysSmoothIfUnitShrinkFactors
>>   - NeverSmoothIfUnitShrinkFactors
>>   - SmoothIfUnitShrinkFactorsAndScheduleDownardDivisible (this being
>> the default for true backwards compatibility)
>>
>> Thoughts anyone?
>>
>> Tom
>>
>> On Wed, Apr 8, 2009 at 23:27, kent williams <norman-k-williams at uiowa.edu>
>> wrote:
>>> It seems Hans assigned me yesterday to fix this 'bug':
>>>
>>> http://www.vtk.org/Bug/view.php?id=7002
>>>
>>> As is noted there, there still doesn't appear to be a consensus on how to
>>> handle this problem.  So I've taken ownership of a bug with no clear way to
>>> fix it.
>>>
>>> If the issue is truly tabled, does it need to hang around as an open bug?
>>>
>>>
>>>
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-- 
Stephen R. Aylward, Ph.D.
Director of Medical Imaging
Kitware, Inc. - North Carolina Office
http://www.kitware.com
(518) 371-3971 x300