[vtkusers] vtkImageData - Set Scalar Components to 1 without corrupting image

[Christian Werner]

Hello! 

I finally managed to implement a vtk2itk2vtk templated class. It 
compiles and basically works, but with one little flaw:

I have to SetNumberOfScalarComponents my vtkImageData to 1 to get the 
itkVTKImporter working, but this clearly distorts my image which has, as 
in many cases, 3 components (RGB...).

The ITK Reference of the itkVTKImageImport states:
"Note that the VTK images are assumed to be of 1, 2, or 3 dimensions. 
Scalar value types can be one of: float, ... The images must have pixel 
types with one component."

The itkVTKImageImport does indeed complain if I don't care and just keep 
the number of pixel components. So the only way for exporting to ITK 
properly seems to be to convert the vtkImageData to data having pixels 
that consist of one component. I do not really know about the philosophy 
of why the itkVTKImporter requests pixels of one component but it 
obviously does. So how can I convert my vtkImageData to the correct 
format without corrupting its content?

I hope this can easily be fixed as I am so happy that after working the 
whole day yesterday on that vtk2itk2vtk stuff I finally got a vtk image 
that goes through this conversion jungle (though distorted). I know 
there is this vtkKWImageIO class but viewing their code didn't help me.

Maybe you want to know how I connect my pipelines, but that should be in 
order:

    typedef itk::VTKImageImport<InputType>     ImageImportType;
    typename ImageImportType::Pointer itkImporter;
    itkImporter = ImageImportType::New();
   
    vtkImageExport* vtkExporter = vtkImageExport::New();
    vtkExporter->SetInput( vtkSourceImage );
   
    //ConnectPipelines( vtkExporter, itkImporter );
    
itkImporter->SetUpdateInformationCallback(vtkExporter->GetUpdateInformationCallback());
    
itkImporter->SetPipelineModifiedCallback(vtkExporter->GetPipelineModifiedCallback());
    
itkImporter->SetWholeExtentCallback(vtkExporter->GetWholeExtentCallback());
    itkImporter->SetSpacingCallback(vtkExporter->GetSpacingCallback());
    itkImporter->SetOriginCallback(vtkExporter->GetOriginCallback());
    
itkImporter->SetScalarTypeCallback(vtkExporter->GetScalarTypeCallback());
    
itkImporter->SetNumberOfComponentsCallback(vtkExporter->GetNumberOfComponentsCallback());
    
itkImporter->SetPropagateUpdateExtentCallback(vtkExporter->GetPropagateUpdateExtentCallback());
    
itkImporter->SetUpdateDataCallback(vtkExporter->GetUpdateDataCallback());
    
itkImporter->SetDataExtentCallback(vtkExporter->GetDataExtentCallback());
    
itkImporter->SetBufferPointerCallback(vtkExporter->GetBufferPointerCallback());
    itkImporter->SetCallbackUserData(vtkExporter->GetCallbackUserData());


Best regards,
Christian