[Insight-users] filter->GetOutput(i) returning NULL

[Ramón Casero Cañas]

On 14/06/12 18:21, Bradley Lowekamp wrote:
> Hello,
>
> You should look at the different types these methods are returning as
> thy are different an sometime incompatible. The warning message says
> what the problem is:
>
> WARNING: In /usr/local/include/ITK-4.1/itkImageSource.hxx, line 112
> DanielssonDistanceMapImageFilter (0x26707d0): dynamic_cast to output
> type failed
>
> These are the methods you should be come familiar with:
>
> OutputImageType * ImageSource::GetOutput (unsigned int idx)
>
> VectorImageType * DanielssonDistanceMapImageFilter::GetVectorDistanceMap
> (void)
>
>
> Then there is:
> DataObject * ProcessObject::GetOutput (const DataObjectIdentifierType &key)
>
> You can perform a dynamic_cast on the return of the ProcessObject's
> method to the correct image type. It is best to check that the result is
> not NULL in case the dynamic_cast fails.


Hi Brad,

Many thanks for your reply. It's not possible to use 
ProcessObject::GetOutput(...) because it's a protected method.

GetVectorDistanceMap() uses a dynamic_cast on 
ProcessObject::GetOutput(...), but for my program I cannot depend on 
specific method names for each filter.

That's why I was trying to use ImageSource::GetOutput(unsigned int idx), 
as it seemed logical that filter->GetOutput(2) would provide the 3rd 
output of the filter.

However, as you say, the output type is itk::ImageSource< TOutputImage 
 >, which is not the type of the VectorDistanceMap. So I don't really 
understand what the purpose of ImageSource::GetOutput(unsigned int idx) is.


I think I just found the solution:

   this->derivedFilter->GetOutputs()[2].GetPointer()

provides the same pointer as

   this->derivedFilter->GetVectorDistanceMap()

Best regards,

Ramon.

-- 
Dr. Ramón Casero Cañas

Computational Biology
Department of Computer Science
University of Oxford
Wolfson Building, Parks Rd
Oxford OX1 3QD

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