How to restore brightness and contrast in VTK?

Question

I am developing a C++ application, using Qt + VTK. Actually, I have a QVTKWidget, used for displaying a DICOM image. I have used a vtkImageViewer2 with a vtkInteractorStyleImage, so I can change brightness and contrast of the image by clicking on it with the mouse, while the left button is pressed.

However, I wish to enable a button for restore brightness and contrast at their original values. I have done some research, but I can't find any function regarding it, in the documentation, nor any saved brightness and contrast value that I can change at run-time.

I hope someone can help. Thank you.

Answer 1

Following this example, I've been able to put this code togheter:

void MainWindow::on_luminosityResetButton_clicked()
{
    vtkSmartPointer<vtkImageShiftScale> shiftScaleFilter = 
    vtkSmartPointer<vtkImageShiftScale>::New();
    shiftScaleFilter->SetOutputScalarTypeToUnsignedChar();
    #if VTK_MAJOR_VERSION <= 5
        shiftScaleFilter->SetInputConnection(imageData->GetProducerPort());
    #else
        shiftScaleFilter->SetInputData(imageData);
    #endif
    shiftScaleFilter->SetShift(0);
    shiftScaleFilter->SetScale(0);
    shiftScaleFilter->Update();

    // Create actors
    vtkSmartPointer<vtkImageSliceMapper> originalSliceMapper = vtkSmartPointer<vtkImageSliceMapper>::New();
    #if VTK_MAJOR_VERSION <= 5
        originalSliceMapper->SetInputConnection(imageData->GetProducerPort());
    #else
        originalSliceMapper->SetInputData(imageData);
    #endif

    vtkSmartPointer<vtkImageSlice> originalSlice = vtkSmartPointer<vtkImageSlice>::New();
    originalSlice->SetMapper(originalSliceMapper);

    vtkSmartPointer<vtkImageSliceMapper> shiftScaleMapper = vtkSmartPointer<vtkImageSliceMapper>::New();
    shiftScaleMapper->SetInputConnection(shiftScaleFilter->GetOutputPort());

    vtkSmartPointer<vtkImageSlice> shiftScaleSlice = vtkSmartPointer<vtkImageSlice>::New();
    shiftScaleSlice->SetMapper(shiftScaleMapper);
    shiftScaleSlice->GetProperty()->SetInterpolationTypeToNearest();

    renderer->AddViewProp(originalSlice);

    vtkSmartPointer<vtkRenderer> shiftScaleRenderer =
        vtkSmartPointer<vtkRenderer>::New();
    shiftScaleRenderer->AddViewProp(shiftScaleSlice);

    ui->qvtkWidget->update();
}

Now it works (brightness and contrast gain their original values), but I have not totally understood the logic behind that. So, I don't mark my own answer as the correct one (hoping to obtain a more pertinent answer), but I post it anyway. I saw this same issue (unanswered) elsewhere, and I hope that it can be useful to others.