[Insight-users] Question on itk::ResampleImageFilter for up and downsampling images

[Lodron, Gerald]

Hello,

I want to write a code to reduce/increase the resolution of an image and i am using the itk::ResampleImageFilter. The code works fine but there is one small problem: When i compare the original and the resampled image with a checkerboard i see that the images are not registered any more (so there must be a problem with the origin). How should i set the origin? Here my code:

Input:

Int *iDownsampleFactor;                                 // = e.g. {2,0.5,4};
Itk::OrientedImage<PixelType ,3>::Pointer image;

Code:

Typedef itk::ResampleImageFilter<InputImageType, OutputImageType, InterpolationPrecisionType> ResampleType;

ResampleType::Pointer  resampler = ResampleType::New();

OutputImageType::SpacingType                    Spacing;
OutputImageType::PointType                      Origin;
OutputImageType::DirectionType          Direction = image->GetDirection();
OutputImageType::SizeType                       Size;
OutputImageType::RegionType::IndexType  Index = image->getLargestPossibleRegion().GetIndex();

For (int i=0; i<3; i++)
{
        Spacing[i] = image->GetSpacing()[i] * iDownsampleFactor[i] ;
        Origin[i] = image->GetOrigin()[i];//????????????????????
        Size[i] = image->GetLargestPossibleRegion().GetSize()[i]/iDownsampleFactor[i] ;
}

Resampler->SetInput(image);
resampler->SetOutputSpacing( Spacing );
resampler->SetOutputOrigin(  Origin  );
resampler->SetOutputDirection(  Direction  );
resampler->SetSize( Size );
resampler->SetOutputStartIndex(  Index );

Output = resampler->GetOutput();        //Wrong alignment/registration to input

Best regards