[Insight-users] coordinate conversion

[Siavash Khallaghi]

What is the format of your point set? Is it vtkPolyData?

Siavash

Petr Jilkine <petr.jilkine at cimtec-canada.ca> wrote:

>Hello,
>
>I have 2 images fixed and moving. I apply some linear transform to
>moving
>image
>to bring it to physical space of fixed image using ResampleImageFilter
>(see
>metacode)
>
>  typedef typename itk::ResampleImageFilter< InputImageType,
>OutputImageType > ResampleFilterType;
>  ResampleFilterType::Pointer resample = ResampleFilterType::New();
>
>  resample->SetInput( moving );
>  resample->SetTransform( transform );
>  resample->SetSize( fixed->GetLargestPossibleRegion().GetSize() );
>  resample->SetOutputOrigin(  fixed->GetOrigin() );
>  resample->SetOutputSpacing( fixed->GetSpacing() );
>  resample->SetOutputDirection( fixed->GetDirection() );
>  resample->SetDefaultPixelValue( zeroValue );
>
>I also have 2 point sets, one in fixed, another in moving image.
>I would like to resample moving point set in a similar way.
>For this I use (metacode)
>
>  typedef itk::TransformMeshFilter< MeshType, MeshType, TransformType >
>TransformMeshType;
>
>TransformMeshType::Pointer movingTransformMesh =
>TransformMeshType::New();
>  movingTransformMesh->SetInput(movingMesh);
>  movingTransformMesh->SetTransform(transform);
>  movingTransformMesh->Update();
>Probably I need to use an inverse transform instead.
>I guess if the points in point sets had world coordinates if would
>work.
>But coordinates of the points are wrt the center of corresponding
>image.
>Now I need to convert these local coordinates to world coordinates
>taking
>into account origin, spacing and direction matrix of the corresponding
>image.
>TransformMeshFilter seems a good candidate to do the job, but it is not
>clear
>how to pass origin, spacing and direction matrix to the filter.
>
>Coordinates conversion like this seems a standard problem and
>I guess there is a standard way to do it in ITK. However, so far
>I couldn’t find an appropriate ITK class/function.
>
>Any advice on this matter is really appreciated.
>
>Thanks,
>Peter Jilkine
>
>
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