[Insight-users] Boundary problem when resampling?

[stan]

I'm using itk 3.14 ...


Le vendredi 13 novembre 2009 à 10:52 -0500, Bill Lorensen a écrit :
> What version of itk are you using?
> 
> On Fri, Nov 13, 2009 at 10:13 AM, stan <stan.oubel at gmail.com> wrote:
> > Dear all,
> >
> > I'm using the ITK resampling filter to upscale 3D images
> > (BSplineInterpolateImageFunction).
> >
> > I encountered two problems with this filter:
> >
> > - there is a misregistration between high-resolution images and
> > resampled low-resolution images. To correct that, I modified the origin
> > ( origin = origin - spacing/2). Now images are well registered,
> >
> > - but now, there is a problem at image boundaries. All voxels close to
> > the boundary (less than spacing/2 in all directions) are set to zero.
> > This is incorrect since the size of the low-resolution have been setup
> > to be exactly a multiple of the high-resolution image size.
> >
> > Here a screenshot and some code I use.
> >
> > Thank you
> >
> > stan
> >
> >
> >
> >  typedef short      PixelType;
> >  const   unsigned int        Dimension = 3;
> >  typedef itk::Image< PixelType, Dimension >    ImageType;
> >  typedef itk::ImageFileReader< ImageType >  ReaderType;
> >  typedef itk::ImageFileWriter< ImageType >  WriterType;
> >  ReaderType::Pointer reader = ReaderType::New();
> >  ReaderType::Pointer reader_input = ReaderType::New();
> >  WriterType::Pointer writer = WriterType::New();
> >
> >  //Reading reference image
> >  reader->SetFileName( reference_file  );
> >  reader->Update();
> >  ImageType::Pointer referenceImage = reader->GetOutput();
> >
> >  //Reading input image
> >  reader_input->SetFileName( input_file  );
> >  reader_input->Update();
> >  ImageType::Pointer inputImage = reader_input->GetOutput();
> >
> >  typedef itk::ResampleImageFilter<ImageType,ImageType> FilterType;
> >  FilterType::Pointer filter = FilterType::New();
> >
> >  typedef itk::AffineTransform< double, Dimension >  TransformType;
> >  TransformType::Pointer transform = TransformType::New();
> >  transform -> SetIdentity();
> >  filter->SetTransform( transform );
> >
> >  typedef itk::BSplineInterpolateImageFunction< ImageType, double, int
> >  >  InterpolatorType;
> >
> >  InterpolatorType::Pointer interpolator = InterpolatorType::New();
> >  interpolator->SetSplineOrder(interp);
> >  filter->SetInterpolator( interpolator );
> >
> >  filter->SetDefaultPixelValue( 0 );
> >
> >  //Initialize with reference image information
> >  filter->SetOutputSpacing( referenceImage->GetSpacing() );
> >
> >  ImageType::SpacingType spacing = inputImage->GetSpacing();
> >  ImageType::PointType origin = inputImage->GetOrigin();
> >  origin[0] -= spacing[0]/2;
> >  origin[1] -= spacing[1]/2;
> >  origin[2] -= spacing[2]/2;
> >
> >  filter->SetOutputOrigin( origin );
> >
> >  filter->SetSize( referenceImage->GetLargestPossibleRegion().GetSize() );
> >
> >  //Do the resampling
> >  filter->SetInput( inputImage );
> >  filter->Update();
> >  ImageType::Pointer outputImage = filter->GetOutput();
> >
> >  //Saving the result
> >  writer->SetFileName( output_file );
> >  writer->SetInput( outputImage );
> >  writer->Update();
> >
> >
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