[vtkusers] How to display dicom images without scaling?

[Joseph D. Wieber Jr.]

Hello,

I'm new to VTK and I'm working on a project that reads dicom image 
files.  The files I have are 512x512 pixels, but when I view them they 
display at approx 150x150 pixels.  I'm using Qt to create the UI via Qt 
designer with the qvtkWidget.  I'm using the vtkImageViewer2 class to 
handle the visualization.  I pasted my initialization code below.  The 
algorithm I'm working on is intelligent scissors (user guided 
segmentation).  I originally implemented it in OpenCV, but need to 
convert my app. to use VTK.  I need to extract pixel locations from left 
click and mouse over events, and I have this part working correctly.  
However, for the algorithm to work properly I need to do a lookup into a 
cost table based on pixel location.  The cost table is built to the 
correct size (512x512), and when I write out the dimensions of the image 
I see 512x512, but when I do the picking I get locations in the range of 
0 - 150.  Indeed, the displayed image takes up only a small portion of 
the widget (see image below).  I tried searching the web and the mailing 
list, but found nothing.  I'm not sure what search terms are 
appropriate.  I found in the vtkImageViewer2 documentation that dicom 
images are scaled by Z coordinate of the image slice.  When I print out 
the position of the image the z coord is 0, but I don't know what (or 
how to get) the position of the camera is.  How can I make the 
visualization pipeline display the image at full size?

Thank you in advance for any help or suggestions.

Regards,

Joseph.

MainWindow::MainWindow( QWidget *parent, const string& fname ) :
     QMainWindow( parent ),
     ui( new Ui::MainWindow ),
     m_fileName( fname )
{
     ui->setupUi( this );

     // Read the image
     vtkSmartPointer< vtkDICOMImageReader > reader =
             vtkSmartPointer< vtkDICOMImageReader >::New();
     reader->SetFileName( m_fileName.c_str () );
     reader->Update ();

     // setup the intelligent scissors object
     //mexican hat LoG
     double laplacian[] = {  0.,  0., -1.,  0.,  0.,
                             0., -1., -2., -1.,  0.,
                            -1., -2., 16., -2., -1.,
                             0., -1., -2., -1.,  0.,
                             0.,  0., -1.,  0.,  0. };

     m_spScissors.reset( new IntelligentScissors( reader->GetOutput (),
                                                  laplacian ) );

     // Setup the blending function to overlay the segmentation contour 
on the image
     vtkSmartPointer< vtkImageBlend > blend =
             vtkSmartPointer< vtkImageBlend >::New();
     blend->AddInputConnection( reader->GetOutputPort() );
     blend->SetOpacity( 0, 0.6 );
     blend->AddInputConnection( m_spScissors->getPathImage () );
     blend->SetOpacity( 1, 0.4 );

     vtkSmartPointer< vtkImageViewer2 > viewer =
             vtkSmartPointer< vtkImageViewer2 >::New();
     viewer->SetInputConnection ( blend->GetOutputPort () );

     // make the viewer use the interactor supplied from the qvtk widget
     viewer->SetupInteractor ( ui->qvtkWidget->GetInteractor () );

     //bind Qt and VTK
     ui->qvtkWidget->SetRenderWindow ( viewer->GetRenderWindow () );

     //try to get image displayed at full size
     viewer->GetInteractorStyle ()->AutoAdjustCameraClippingRangeOff ();

     // Annotate the image with mouse over pixel information
     vtkSmartPointer< vtkCornerAnnotation > cornerAnnotation =
             vtkSmartPointer< vtkCornerAnnotation >::New();
     cornerAnnotation->SetLinearFontScaleFactor( 2 );
     cornerAnnotation->SetNonlinearFontScaleFactor( 1 );
     cornerAnnotation->SetMaximumFontSize( 15 );
     cornerAnnotation->SetText( 0, "Off Image" );
     cornerAnnotation->SetText( 3, "<window>\n<level>" );
     cornerAnnotation->GetTextProperty()->SetColor( 1, 0, 0 );
     viewer->GetRenderer ()->AddViewProp ( cornerAnnotation );

     // Picker to pick pixels
     vtkSmartPointer< vtkPropPicker > propPicker =
             vtkSmartPointer< vtkPropPicker >::New();
     propPicker->PickFromListOn();

     // Give the picker a prop to pick
     vtkImageActor* imageActor = viewer->GetImageActor();
     propPicker->AddPickList( imageActor );

     // disable interpolation, so we can see each pixel
     imageActor->InterpolateOff();

     // Set callback functions
     vtkInteractorStyleImage* imageStyle = viewer->GetInteractorStyle();

     //listen to MouseMoveEvents invoked by the interactor's style
     OnMouseMovePtr onMouseMove = OnMouseMovePtr::New();
     onMouseMove->SetViewer( viewer );
     onMouseMove->SetAnnotation( cornerAnnotation );
     onMouseMove->SetPicker( propPicker );
     onMouseMove->SetIntelligentScissors ( m_spScissors );
     imageStyle->AddObserver( vtkCommand::MouseMoveEvent, onMouseMove );

     //listen to LeftButtonPressEvent invoked by the interactor's style
     OnLeftClickPtr onLeftClick = OnLeftClickPtr::New ();
     onLeftClick->SetViewer ( viewer );
     onLeftClick->SetAnnotation ( cornerAnnotation );
     onLeftClick->SetPicker ( propPicker );
     onLeftClick->SetIntelligentScissors ( m_spScissors );
     imageStyle->AddObserver ( vtkCommand::LeftButtonPressEvent, 
onLeftClick );

     viewer->Render ();
}


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