[Insight-users] itk::StatisticsLabelMapFilter with input image size != feature image size

[Arnaud GELAS]

Hi Gaetan,

You're right, this is a general problem!

We could add conditions on origin, spacing, direction in such filters, 
and use the current implementation; else we could either use 
TransformPhysicalPoint as Luis suggested, either throw an exception. 
This would impact a lot of filters.

Thoughts?

Best,
Arnaud

On 12/10/2010 09:40 AM, Gaëtan Lehmann wrote:
> Hi,
>
> Yes, the image must have the same origin, spacing and direction.
> It should be possible to have a larger feature image than the label
> map, but that's all.
>
> This is a very usual requirement in the ITK filters, and I think that
> most of them have this constraint.
> Pixels are accessed through their index, not their physical position.
> If the images are not aligned, it becomes a bit more difficult to
> access the data.
>
> I think the question of whether we should do that or not is not
> specific to that filter, but should be discussed for all the filters
> which are using more than one input - for example
> itk::BinaryFunctorImageFilter
>
> Regards,
>
> Gaëtan
>
>
> Le 10 déc. 10 à 13:12, Luis Ibanez a écrit :
>
>> Hi Arnaud,
>>
>> Given that the algorithm visits all the pixels
>> from the lines of the label objects and use
>> them to query the feature image in line:
>>
>> itkStatisticsLabelMapFilter.txx:120
>>
>> const FeatureImagePixelType&  v = featureImage->GetPixel(idx);
>>
>> it would seem that we just need to insert the guard:
>>
>> if( ! featureImage->GetBufferedRegion().IsInside( idx ) ) continue;
>>
>> just before the GetPixel line.
>>
>>
>> Then, the statistics will be computed using only the overlapping
>> regions between the LabelMap and the feature image.
>>
>> Yet, a more tempting option is to let the feature image be of
>> any origin, spacing and orientation by introducing the
>> following code:
>>
>> labelMap->TransformIndexToPhysicalPoint( idx, ptx );
>> bool isInside = featureImage->TransformPhysicalPointToIndex( ptx,
>> idx2 );
>> if( ! isInside ) continue;
>> const FeatureImagePixelType&  v = featureImage->GetPixel(idx);
>>
>>
>> There is a price in computation time,...
>> but the added generality seem to be worth it.
>>
>>
>>     Luis
>>
>>
>> ---------------------------------------------
>> 2010/12/9 Gelas, Arnaud Joel Florent<Arnaud_Gelas at hms.harvard.edu>:
>>> Vince,
>>>
>>> Thanks for your reply!
>>>
>>> That's also what I thought; but I got some code from a student with
>>> such a case. The code does not fail, and even provides results
>>> (most probably not the right ones, but it does).
>>>
>>> Would it be possible to add exceptions to handle these cases
>>> (different origin, spacing, etc...) if it is not supposed to work ?
>>>
>>> Thanks,
>>> Arnaud
>>> ________________________________________
>>> From: Magnotta, Vincent A [vincent-magnotta at uiowa.edu]
>>> Sent: Wednesday, December 08, 2010 10:13 PM
>>> To: Gelas, Arnaud Joel Florent; Gaëtan Lehmann
>>> Cc: ITK Users
>>> Subject: RE: [Insight-users] itk::StatisticsLabelMapFilter with
>>> input image size != feature image size
>>>
>>> Arnaud,
>>>
>>> My reading of the algorithm is that the images must be of the same
>>> size, spacing, directions, and origin to work correctly.
>>>
>>> Vince
>>>
>>>
>>> ----------------------
>>> Associate Professor
>>> Department of Radiology
>>> 0453-D JCP
>>> 200 Hawkins Drive
>>> Iowa City, IA 52242
>>> E-mail: vincent-magnotta at uiowa.edu
>>> Phone: 319-356-8255 Fax: 319-353-6275
>>> Website: http://www.radiology.uiowa.edu
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: insight-users-bounces at itk.org on behalf of Arnaud GELAS
>>> Sent: Wed 12/8/2010 3:45 PM
>>> To: Gaëtan Lehmann
>>> Cc: ITK Users
>>> Subject: [Insight-users] itk::StatisticsLabelMapFilter with input
>>> image size != feature image size
>>>
>>> Hi Gaetan,
>>>
>>> In itk::StatisticsLabelMapFilter, does the feature image need to be
>>> aligned (same origin, same spacing) with the input one?
>>>
>>> For instance, can you use this filter with a feature image larger
>>> than
>>> the input one, i.e. the input one is a ROI from one label map with
>>> same
>>> spacing, origin from the feature image?
>>>
>>> Thanks,
>>> Arnaud
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