[vtkusers] vtkResliceImageViewer: changing Window/Level contrast question

[Audrius Stundzia]

Hello vtk users,



Have run into a problem/puzzle with regards to the Window/Level
adjustment settings in vtkResliceImageViewer.

[It's a very useful class, btw, so thanks to it's developers.]



I've attached 2 example images that illustrate the issue. PET as the
effect is most dramatic ;-)

The same issue occurs for other modalities: MR and CT.



The code [relevant fragment is below] reads the DICOM data and displays
it as expected [re PT_before.jpg].



However, when the left mouse button is pressed and the icon is moved,
rather then the expected minor change

in the Window/Level settings, there is a very large change [re
PT_after.jpg].



So,



Is there something missing or wrong from the code below?



Is the Window/Level change functionality missing
from vtkResliceImageViewer?



Is there a callback that I need to add? If so, is there a sample code
fragment somewhere?



Any insight would be appreciated.



Audrius





OS: Windows 7 x64

vtk: 5.10.1

compiler: VS 2008 version 9 [x64]



Code fragment:



vtkSmartPointer<vtkGDCMImageReader> imageReader =
vtkSmartPointer<vtkGDCMImageReader>::New();



// . . . gets the DICOM data here



// Scalar image data display

vtkSmartPointer<vtkResliceImageViewer> resliceImageViewer =
vtkSmartPointer<vtkResliceImageViewer>::New();

resliceImageViewer->SetInput( imageReader->GetOutput()); //



std::string dicomModality =
imageReader->GetMedicalImageProperties()->GetModality();



if( dicomModality == "PT" ||

    dicomModality == "NM" ||

    dicomModality == "ST" )

{

    std::cout << "DICOM modality: " << dicomModality << std::endl;



    double window;

    double level;



    imageReader->GetMedicalImageProperties()->GetNthWindowLevelPreset (
0, &window, &level );



   // A colour map of {r, g, b} triplets

   boost::scoped_ptr<aRainbowColourMap> rainbowColourMapPtr(new
aRainbowColourMap);



   const vtkIdType nColours =
static_cast<vtkIdType>(rainbowColourMapPtr->GetNColours()); // 256
colours



   vtkSmartPointer<vtkWindowLevelLookupTable> windowLevelLookupTable =
vtkSmartPointer<vtkWindowLevelLookupTable>::New();

   windowLevelLookupTable->SetWindow( window);

   windowLevelLookupTable->SetLevel( level);

   windowLevelLookupTable->SetNumberOfTableValues( nColours);



   for( vtkIdType iC = 0; iC < nColours; ++iC)

   {

      double r; double g;  double b;



      rainbowColourMapPtr->GetRGB( iC, r, g, b );



      windowLevelLookupTable->SetTableValue( iC, r, g, b, 1.0 );

   }



   windowLevelLookupTable->SetRampToLinear();

   windowLevelLookupTable->Build();



   resliceImageViewer->SetLookupTable( windowLevelLookupTable);

}

else

if( dicomModality == "MR" )

{



   // . . . Analogous code for MR here



}

else

if( dicomModality == "CT" )

{

   // . . .  Analogous code for CT here

}



vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();



// Callback functions

// 1/ Close and exit vtk window

vtkSmartPointer<vtkCallbackCommand> keypressCallback =
vtkSmartPointer<vtkCallbackCommand>::New();

keypressCallback->SetCallback( KeypressCallbackFunction);

renderWindowInteractor->AddObserver( vtkCommand::KeyPressEvent,
keypressCallback );



resliceImageViewer->SetupInteractor( renderWindowInteractor);



// Initialize rendering and interaction

resliceImageViewer->GetRenderWindow()->SetSize( 900, 900 );

resliceImageViewer->GetRenderer()->SetBackground( 0.0, 0.0, 0.0 );



resliceImageViewer->GetRenderer()->ResetCamera();

resliceImageViewer->SliceScrollOnMouseWheelOn();

resliceImageViewer->Render();



renderWindowInteractor->Initialize();

renderWindowInteractor->Start();
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