[Insight-users] Boundary problem when resampling?

[Bill Lorensen]

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();
>
>
> _____________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Kitware offers ITK Training Courses, for more information visit:
> http://www.kitware.com/products/protraining.html
>
> Please keep messages on-topic and check the ITK FAQ at:
> http://www.itk.org/Wiki/ITK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.itk.org/mailman/listinfo/insight-users
>
>