[Insight-users] Simple resampling problem

[Richard Beare]

Hi,
I'm using an obviously buggy resampling procedure to upsample a small
image that has been extracted from a larger one, and hence has non
zero origin information. My result is blank, so I'm missing a setting
somewhere, but don't have a clue as to what. Can anyone spot the
problem?

template  <class RawIm>
typename RawIm::Pointer upsampleIm(typename RawIm::Pointer input,
typename RawIm::SpacingType NewSpacing, int interp=1)
{
  const int dim = RawIm::ImageDimension;
  typedef typename RawIm::PixelType PixelType;

  typedef typename itk::ResampleImageFilter<RawIm, RawIm >  ResampleFilterType;
  typedef typename itk::IdentityTransform< double, dim >  TransformType;
  typename ResampleFilterType::Pointer resampler = ResampleFilterType::New();

  input->Update();

  typename TransformType::Pointer transform = TransformType::New();
  transform->SetIdentity();
  resampler->SetTransform( transform );
  typedef typename itk::LinearInterpolateImageFunction<RawIm, double >
 LInterpolatorType;
  typedef typename itk::NearestNeighborInterpolateImageFunction<RawIm,
double >  NNInterpolatorType;

  typename ResampleFilterType::InterpolatorPointerType interpolator;
  switch (interp)
    {
    case 0:
      interpolator = NNInterpolatorType::New();
      break;
    case 1:
      interpolator = LInterpolatorType::New();
      break;
    default:
      std::cout << "Unsupported interpolator" << std::endl;
    }

  resampler->SetInterpolator( interpolator );
  resampler->SetDefaultPixelValue( 0 );

  const typename RawIm::SpacingType& inputSpacing = input->GetSpacing();
  typename RawIm::SpacingType spacing;
  typename RawIm::SizeType   inputSize =
input->GetLargestPossibleRegion().GetSize();
  typename RawIm::SizeType   size;
  typedef typename RawIm::SizeType::SizeValueType SizeValueType;


  for (int i = 0; i < dim; i++)
    {
    float factor = inputSpacing[i]/NewSpacing[i];
    size[i] = static_cast< SizeValueType >( inputSize[i] * factor );
    }
   std::cout << inputSpacing << NewSpacing << std::endl;
   std::cout << inputSize << size << input->GetOrigin() << std::endl;

  resampler->SetSize( size );
  resampler->SetOutputSpacing( NewSpacing );
  resampler->SetOutputOrigin( input->GetOrigin() );
  resampler->SetOutputDirection(input->GetDirection());
  resampler->SetInput(input);
  typename RawIm::Pointer result = resampler->GetOutput();
  result->Update();
  result->DisconnectPipeline();
  return(result);
}

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