[Insight-users] interpolating VariableLengthVectors?

[Luis Ibanez]

Hi George,


This is a "bug" in the VectorLinearInterpolateImageFunction,
we should be using the Traits

           MeasurementVectorTraits::GetLength( x2 )


Instead of assuming that the pixel type has a  "Dimension" trait.

So, we should remove from  itkVectorInterpolateImageFunction.h

the statement in line 65-66

  itkStaticConstMacro(Dimension, unsigned int,
                      TInputImage::PixelType::Dimension);

and remove from itkVectorLinearInterpolateImageFunction.h

the lines  66-67

  itkStaticConstMacro(Dimension, unsigned int,
                       Superclass::Dimension);

and finally, in itkVectorLinearInterpolateImageFunction.txx

we should replace line 141:

    for(unsigned int k = 0; k < Dimension; k++ )

with

    for(unsigned int k = 0; k < vectorDimension; k++ )

and insert just after line 140 something like:

const unsigned int vectorDimension =
           MeasurementVectorTraits::GetLength( input );


With these changes, the vector linear interpolator
should be compatible with VariableLength vector as a
pixel type.


    Could you please give it a try at these changes,
    and let us know if they work for you ?

    If so we will commit them in the CVS repository.


        Thanks


              Luis


--------------------------------------------


On Thu, Feb 4, 2010 at 11:47 AM, g c <gc12358 at googlemail.com> wrote:
> Hi,
>
> I use the following 'solution' for interpolating a VectorImage by
> using the VectorImageToImageAdaptor and interpolating each component
> separately:
>
> =======================
>
> unsigned int Dimension = 3;
> typedef float DataType;
> typedef itk::VectorImage< DataType, Dimension > VectorImageType;
> typedef itk::VectorImageToImageAdaptor< DataType, Dimension >
> VectorImageToImageAdaptorType;
> typedef itk::LinearInterpolateImageFunction<
> VectorImageToImageAdaptorType, DataType >
> LinearInterpolateImageFunctionType;
>
> VectorImageToImageAdaptorType::Pointer Adaptor =
> VectorImageToImageAdaptorType::New();
> LinearInterpolateImageFunctionType::Pointer Interpolator =
> LinearInterpolateImageFunctionType::New();
>
> VectorImageType::Pointer VectorImage = VectorImageType::New();
>
> ...
>
> for( unsigned int i=0; i<NrOfComp; i++)
> {
>    Adaptor->SetExtractComponentIndex( i );
>    Adaptor->SetImage( VectorImage );
>    Adaptor->Update();
>    Interpolator->SetInputImage( Adaptor );
>
>    PointsContainerIteratorType Iter = m_PointsContainer->Begin();
>    unsigned int PointId = 0;
>    while( Iter != m_PointsContainer->End()  )
>    {
>        m_Data[PointId][i] = Interpolator->Evaluate( Iter.Value() );
>        Iter++;
>        PointId++;
>    }
> }
>
> =======================
>
> I would still be interested if anyone knows a more direct/better way
> of interpolating an itk::VectorImage.
>
> cheers,
>
> George
>
>
> On 1 February 2010 13:29, g c <gc12358 at googlemail.com> wrote:
>> Dear all,
>> I may have missed this when looking through the itk documentation, but is
>> there a way to interpolate the VariableLengthVectors in a VectorImage?
>> I've tried:
>>     typedef float DataType;
>>     typedef itk::VectorImage< DataType, 3 > VectorImageType;
>>     typedef itk::VectorLinearInterpolateImageFunction< VectorImageType,
>> DataType > VectorImageInterpolatorType;
>> but when I instantiate the interpolator using
>>     VectorImageInterpolatorType::Pointer CoefficientsInterpolator =
>> VectorImageInterpolatorType::New();
>> I get the error 'Dimension' is not a member of
>> 'itk::VariableLengthVector<mm::DataType>'
>> So I guess VectorLinearInterpolateImageFunction can only be used for
>> FixedArray pixel types?
>> Is there an itk interpolator that can deal with VariableLengthVectors? Any
>> suggestions welcome!
>> Thanks,
>> George
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