[vtkusers] Error messages and no image with vtkImageViewer2

[Jan]

Hi,

I am writing a little QT application using ITK and VTK, trying to use 
vtkIMageViewer2.

During startup, I get the following error messages:

ERROR: In VTK-504/Filtering/vtkDemandDrivenPipeline.cxx, line 710
vtkStreamingDemandDrivenPipeline (0x11b8570): Input port 0 of algorithm 
vtkImageMapToWindowLevelColors(0x118dc50) has 0 connections but is not 
optional.

ERROR: In VTK-504/Rendering/vtkImageActor.cxx, line 182
vtkOpenGLImageActor (0x11bfaf0): This filter requires unsigned char 
scalars as input

And the view keeps blank


=============================================================
Code:
=============================================================
ViewingWidget.h:
...
QVTKWidget _view;
...

ViewingWidget.cpp:
...
ViewingWidget::ViewingWidget( const char* name) :
     QWidget()
{
     _imageViewer = vtkImageViewer2::New();
     _view.setParent( this );
     _view.SetRenderWindow( _imageViewer->GetRenderWindow() );
     _imageViewer->SetupInteractor( 
_view.GetRenderWindow()->GetInteractor() );
     _imageViewer->SetColorLevel( 100 );
     _imageViewer->SetColorWindow( 256 );
}
...

loading the image comes later when pressing a button.

typedef itk::Image< unsigned char, 3 > ImageType;
typedef itk::ImageSeriesReader< ImageType > ReaderType;
typedef itk::ImageToVTKImageFilter< ImageType > FilterType;

ImageType::Pointer image;
ReaderType::Pointer reader = ReaderType::New();
FilterType::Pointer itk2vtk;
...
reader->SetFileNames( names );
reader->Update();
image = reader->GetOutput();

itk2vtk->SetInput( image );
_imageViewer->SetInput( itk2vtk->GetOutput() );
=============================================================

when I use

     vtkPNGReader* reader = vtkPNGReader::New();
     reader->SetFileName( "image.png" );
     _imageViewer->SetInputConnection( reader->GetOutputPort() );

it shows me a grayscale pattern that does not really look like the input 
image.

=============================================================

It would be great if you could give me a hint how to properly use 
vtkImageViewer2.

Thanks,
Jan


VTK: 5.0.4
ITK: 3.4.0
QT:  4.3
gcc: 4.2.1 (SUSE Linux)
OpenSuSE 10.3 64bit