[Insight-users] VTKImageImport - Input Components Mayhem

[Christian Werner]

Gee, that's embarassing. All the headache just because I did not know 
how to properly set up RGB PixelTypes in ITK. But one thing was really 
irritating and working against me:

The ITK Reference on the itkVTKImageImporter 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."

Do I misunderstand something here?? "The Images must have pixel types 
with one component", what does that mean? I nearly spammed the VTK 
Mailing List on how to convert vtkImageData to Data which have one 
scalar component per pixel...
The other irritating thing was that I found one post where somebody told 
the poster to use SetNumberOfScalarComponents(1) before importing to 
ITK. That is not a good choice, because you corrupt your data that way...

Anyway I am glad everything works fine. In case somebody wants to know:

  typedef itk::RGBPixel< unsigned char >        PixelType;
  typedef itk::Image<PixelType, DIM>    InputType;

that does the trick and any itkVTKImageImporter instantiated that way is 
happy with RGB images from VTK!

Are there still more PixelTypes I have to account for?


Best regards,
Christian



Christian Werner wrote:
> Hi Luis!
>
> I am instatiating according to what I get from
>
> vtkInput->GetDataDimension();
> vtkInput->GetScalarTypeAsString();
>
> and (DIM is a template parameter)
>
>    if (strcmp("unsigned char", scalarTypeString) == 0) {
>    typedef itk::Image<unsigned char, DIM>    InputType;
>    return applyConversion<InputType>(vtkOutImage);   //return 
> vtkImageData*
>    ...
>
> and then I call my templated conversion functions, which instantias 
> the Importer:
>
> template <typename InputType>
> applyConversion(vtkImageData* vtkSourceImage)
> {
>    //vtkErrorMacro(<<"Applying Conversion...");
>
>    typedef itk::VTKImageImport<InputType>     ImageImportType;
>    typename ImageImportType::Pointer itkImporter;
>    itkImporter = ImageImportType::New();
>      vtkImageExport* vtkExporter = vtkImageExport::New();
>    vtkExporter->SetInput( vtkSourceImage) );
>   ...ConnectPipelines...
> }
>
> =>corrupted ITK image or
>
> (ERROR: VTKImageImport(0x22900f0): Input number of components is 3 but
> should be 1)
>
> if I do not set the number of scalar components to 1.
>  
> So I don't really have any influence here. Is there some information 
> that I am missing? Aren't the number of components passed by the 
> SetNumberOfComponentsCallback(...) in the ConnectPipelines?
>
> Best regards,
> Christian
>
>
>
> Luis Ibanez wrote:
>> Hi Christian,
>>
>> Does your image actually has 3 components ?
>>
>> Are you instantiating the ITK image with a pixel
>> type that has 3 components ?
>>
>> The typedef for the ITK image was not included
>> in your email.
>>
>>
>>     Please let us know,
>>
>>
>>            Thanks
>>
>>
>>                Luis
>>
>>
>> ----------------------------------------------------
>> On Mon, Feb 15, 2010 at 4:04 PM, Christian Werner
>> <christian.werner at rwth-aachen.de> wrote:
>>  
>>> Hello!
>>>
>>> At first I want to thank Arunachalam and Wagner for their responses 
>>> on my
>>> last thread, thanks! :-) I finally managed to implement my vtk2itk2vtk
>>> templated super-class. It works with one little flaw:
>>>
>>> I have to SetNumberOfScalarComponents my vtkImageData to 1 before going
>>> through the whole conversion loop...
>>> (ERROR: VTKImageImport(0x22900f0): Input number of components is 3 but
>>> should be 1)
>>>
>>> This is bad, because the image content is clearly corrupted that 
>>> way. It
>>> goes well through my vtk2itk2vtk and I can save a result vtk image, 
>>> but this
>>> is distorted, as I fiddled around with these scalar components. Also 
>>> the ITK
>>> filters I want to use on my import complain about
>>>
>>> ERROR: In /opt/ParaView3/VTK/Filtering/vtkImageData.cxx, line 1473
>>> vtkImageData (0x228afd0): GetScalarPointer: Pixel (0, 0, 0) not in 
>>> memory.
>>> Current extent= (0, -1, 0, -1, 0, 0)
>>>
>>>
>>> This is how my pipelines connect:
>>>
>>> template <typename VTK_Exporter, typename ITK_Importer>
>>> void ConnectPipelines(VTK_Exporter* exporter, ITK_Importer importer)
>>> {
>>>  importer->SetUpdateInformationCallback(exporter->GetUpdateInformationCallback()); 
>>>
>>>  importer->SetPipelineModifiedCallback(exporter->GetPipelineModifiedCallback()); 
>>>
>>>  importer->SetWholeExtentCallback(exporter->GetWholeExtentCallback());
>>>  importer->SetSpacingCallback(exporter->GetSpacingCallback());
>>>  importer->SetOriginCallback(exporter->GetOriginCallback());
>>>  importer->SetScalarTypeCallback(exporter->GetScalarTypeCallback());
>>>  importer->SetNumberOfComponentsCallback(exporter->GetNumberOfComponentsCallback()); 
>>>
>>>  importer->SetPropagateUpdateExtentCallback(exporter->GetPropagateUpdateExtentCallback()); 
>>>
>>>  importer->SetUpdateDataCallback(exporter->GetUpdateDataCallback());
>>>  importer->SetDataExtentCallback(exporter->GetDataExtentCallback());
>>>  importer->SetBufferPointerCallback(exporter->GetBufferPointerCallback()); 
>>>
>>>  importer->SetCallbackUserData(exporter->GetCallbackUserData());
>>> }
>>>
>>> I hope this can easily be fixed as I am so happy that after working the
>>> whole day on that vtk2itk2vtk stuff I finally got a vtk image that goes
>>> through this conversion jungle. How can it be equipped to survive this
>>> adventure undistorted?
>>>
>>>
>>> Best regards,
>>> Christian
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>
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>
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>
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