[Insight-developers] Modifying MaskImageFilter to work on VectorImage

Tue Apr 12 01:33:29 EDT 2011

Hi Gaëtan,

Thank you for your thoughtful comments.

2011/4/11 Gaëtan Lehmann <gaetan.lehmann at jouy.inra.fr>:
>
> Hi Cory,
>
> I think this code would fail if the mask filter is run a second time with a
> vector image with a different number of components.
> There should be a check for the number of components in
> BeforeThreadedGenerateData().

Yes, it would be good to check that the number of components in the
OutsideValue matches the number in the image, throwing an exception if
the number of components doesn't match.

> The initialization of the default value of OutsideValue is quite
> problematic, as it can be done only when the number of components is known.

Agreed!

> A better option would be to have a way to say "I want to use the default
> value" - in that case the value can be generated in
> BeforeThreadedGenerateData() and would fit the vector the filter is
> currently working on - or "I want to use that value" and then it is the
> responsibility of the user to provide the right number of components.
>
> One way to implement that is to use a 3rd input for the filter which would
> be of type
>
>  SimpleDataObjectDecorator< PixelType >
>
> and to not provide a default value by default - just keep the 3rd input as
> NULL. If there is no 3rd input, then the default value of OutsideValue can
> be generated in BeforeThreadedGenerateData(). If there is a 3rd input, then
> just use the value provided.

While your suggestion sounds reasonable, the same behavior can also be
achieved using the current ITK norm of setting filter constants via a
method. All it would take would be to examine the OutsideValue to see
if it is zero length or if it consists of all zeros, and if so, infer
that the user wants to use the default value with the correct number
of components. To get back to the "default" value, all the user would
have to do is set the OutsideValue to some vector of zeros or a
zero-length vector. Does that seem reasonable?

> An additional benefit of that approach: the OutsideValue can be provided
> through the pipeline, which is not the case currently.

I think that your notion of treating filter constants as inputs to the
pipeline is very interesting and has merit, but I'll defer to more
experienced developers to determine if that is where ITK should be
heading.

Thanks,
Cory

>
>
> Le 11 avr. 11 à 07:30, Cory Quammen a écrit :
>
>> David and Luis,
>>
>> I have posted a potential solution on github.
>>
>>
>> https://github.com/cquammen/ITK/commit/a92bcc79f267d79f48abb7358881c4b2323ae01d
>>
>> I will post it to gerrit if you don't see any showstoppers.
>>
>> Thanks,
>> Cory
>>
>> On Sun, Apr 10, 2011 at 5:50 PM, Luis Ibanez <luis.ibanez at kitware.com>
>> wrote:
>>>
>>> Hi David,
>>>
>>> We have been discussing this problem with Julien Malik from the
>>> Orfeo Toolbox team.
>>>
>>> In summary, there is a function in the NumericTraits that is intended
>>> to deal with management of size in containers of variable size
>>> such as the VariableLengthVector and the std::vector.
>>>
>>> Regarding your questions, please see below.
>>>
>>> On Thu, Apr 7, 2011 at 7:50 PM, David Doria <daviddoria at gmail.com> wrote:
>>>>
>>>> We have been having some discussion on the best way to allow
>>>> MaskImageFilter
>>>> to work on VectorImage (with pixels of type VariableLengthVector) . The
>>>> problem is that the length of a VariableLengthVector is not defined at
>>>> compile time. This means that in the MaskInput functor, the
>>>> member m_OutsideValue cannot be initialized.
>>>>
>>>> Brad has identified two problems,
>>>>
>>>> 1) How do we initialized the member variable in the functor?
>>>>
>>>
>>> We usually add "Set" methods to the functor,
>>> the add "Set" methods to the Filter itself,
>>> and they simply call the "Set" methods of the functor.
>>>
>>>> This seems to be the main issue I'm not sure how to address.
>>>>
>>>> 2) When do we detect the size of the vector image, and use reasonable
>>>> defaults?
>>>>
>>>
>>>
>>> At run time,
>>> by asking them for their "GetNumberOfComponents()
>>> from the vector image.
>>>
>>> Reasonable default (otherwise) is "1".
>>>
>>>> We think this could be done in BeforeThreadedGenerateData.
>>>>
>>>
>>> Yes, that's a good place.
>>>
>>> The GenerateInputInformation() or
>>> GenerateOutputInformation() may
>>> be good places as well.
>>>
>>>
>>>> The complete conversation is here:
>>>>
>>>> http://review.source.kitware.com/#change,1338
>>>> Any thoughts are welcome!
>>>> Thanks,
>>>>
>>>> David
>>>>
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>>
>>
>>
>> --
>> Cory Quammen
>> Computer Integrated Systems for Microscopy and Manipulation (CISMM)
>> Department of Computer Science
>> University of North Carolina at Chapel Hill
>> http://www.cs.unc.edu/~cquammen
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Kitware offers ITK Training Courses, for more information visit:
>> http://kitware.com/products/protraining.html
>>
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>
> --
> 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
>
>

-- 
Cory Quammen
Computer Integrated Systems for Microscopy and Manipulation (CISMM)
Department of Computer Science
University of North Carolina at Chapel Hill
http://www.cs.unc.edu/~cquammen