[Insight-developers] Proposed requirements for convolution filters in ITK

[Gaëtan Lehmann]

Le 1 juin 11 à 22:12, Cory Quammen a écrit :

>>> Here is what I would like to see in the convolution filters in ITK.
>>>
>>> - Convolution filters should have the same interface to make it easy
>>> to switch between the spatial domain and Fourier domain methods.  
>>> This
>>> suggests a class hierarchy for image convolution filters, perhaps
>>> organized as follows:
>>>
>>> --ConvolutionImageFilter
>>> ---SpatialDomainConvolutionImageFilter
>>> ---FourierDomainConvolutionImageFilter
>>>
>>
>> Looks like a good idea, even if I would prefer some shorter names
>
> Any suggestions for shorter names?

No. I'm really bad at that :-)

>>
>>> - The user must have the ability to specify which index is treated  
>>> as
>>> the center of the second input. This should default to
>>> floor((2*index+size-1)/2) where index and size are from the largest
>>> possible region of the kernel image input.
>>
>> Can you give a use case for that feature?
>
> Say I'm synthesizing some images to test deconvolution algorithms, and
> the center of my microscope point-spread function does not correspond
> to the central image index. I'd like to specify the index that should
> be treated as the center of the PSF image rather than crop or resample
> the PSF image.
>
> This was initially motivated by the question of what to do when the
> kernel size is even. Where do you center it? I think the filters
> should automatically determine a center for convenience, but if the
> user disagrees with the choice of the center made by the filter, s/he
> should be able to specify the desired index that is treated as the
> center. Without this feature, a user might need to change the size of
> the kernel image by padding or cropping to accomodate the filter's
> definition of the kernel center.
>

It looks like a very valid usage. My only concern is that this index  
may not work well with the pipeline.
I guess that if the default value is computed for each kernel size  
then that's ok.

> Alternatively, we could say that the center of the kernel is defined
> to be index (0, 0, ... 0) and force the user to change the image
> information to achieve the desired centering, but that seems like a
> lot of work. It is simpler to specify which image index to treat as
> the kernel center in the convolution filter directly.

I do prefer the index option.

Gaëtan


-- 
Gaëtan Lehmann
Biologie du Développement et de la Reproduction
INRA de Jouy-en-Josas (France)
tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
http://voxel.jouy.inra.fr  http://www.itk.org
http://www.mandriva.org  http://www.bepo.fr

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