[Insight-developers] Re: VectorImage class in the pipeline

[Jim Miller]

Thanks Karthik. UnaryFunctor provides GenerateOutputInformation
because the input and output can be different dimensions. You can use
it to cast from a 2d to a 3d image.  - Jim

On 2/8/07, Karthik Krishnan <karthik.krishnan at kitware.com> wrote:
> On 2/8/07, Jim Miller <millerjv at gmail.com> wrote:
> >
> > It looks to me like the VectorImage class has not been integrated in the
> > ITK pipeline.  For example, one cannot put a VectorImage through a
> > CastImageFilter to
>
>
> You can now. For most filters (on which it makes sense), VectorImages do
> work.
>
> The ProcessObject propagates VectorLength through the pipeline via the
> following line in its GenerateOutputInformation() method :
>   output->CopyInformation(input)
> and ImageBase copies the VectorLength over in line 244.
>   SetNumberOfComponentsPerPixel(imgData->GetNumberOfComponentsPerPixel() )
>
> I overlooked UnaryFunctorImageFilters, which override the
> GenerateOutputInformation() method and unlike most other filters, do not
> call the superclass GenerateOutputInformation() method. Is there a reason, I
> wonder ?
>
> So I added just added this line in UnaryFunctorImageFilter and they work
> fine for VectorImage.
> http://www.itk.org/cgi-bin/viewcvs.cgi/Code/BasicFilters/itkUnaryFunctorImageFilter.txx?root=Insight&r1=1.30&r2=1.31
>
> The CastImageFilter is a simple subclass of the UnaryFunctorImageFilter, so
> > I am guessing that none of the subclasses of UnaryFunctorImageFilter,
> > BinaryFunctorImageFilter, etc. can handle a VectorImage.
>
>
> Subclasses of BinaryFunctorImageFilter do work fine. I just tried
> itk::AddImageFilter. The ProcessObject::GenerateOuptutInformation takes care
> of it.
>
> This is very disappointing since we have many such subclasses and they
> > provide the very basics of pixel manipulation. (No neighborhoods are
> > evaluated, etc.)
>
>
> Karthik, I though you went through a large number of the filters to make to
> > make them work for VectorImage.  Are these filters on the roadmap?
>
>
> Generally speaking, if a filter works on
> Image< itk::Array< T >, N >, it should work with VectorImages as well, since
> they are supposed to provide the same external API as the former, internally
> maintaining a non-fragmented memory layout. If it doesn't, that's bad.
>
> The basis of the issue is that the vector length is not part of the
> > information configured by a filter when GenerateOutputInformation is
> called.
> > So the output image is never configured with an appropriate VectorLength
> and
> > the Allocate() method ends making vectors which are zero length).
>
>
> You're right. For filters that override GenerateOutputInformation and do not
> call the superclass method, its a problem. Most filters called the
> superclass method. There are a few filters that don't and they need to
> propagate VectorLength down just as they propagate regions down themselves.
> It just requires one additional line on all filters that don't:
>
> outputPtr->SetNumberOfComponentsPerPixel(inputPtr->GetNumberOfComponentsPerPixel());
>
> I'll add that.
>
> Sorry for the overlook and thanks for pointing this out.
>
> Thanks
> --
> karthik
>