[Paraview] TexturePainter missing Scalar Data

[Christian Werner]

Hello!

I use the vtkSimpleImageToImageFilter to make a nifty little 
segmentation plugin. Below is how I overwrote the SimpleExecute 
function. It looks good and actually does the job, at least in a 
VTK-only (Reader>MyFilter>Writer) setup. It loads in Paraview, but if 
executed I get the following warning and bad/no (visual) results:

Warning: In /opt/ParaView3/Servers/Filters/vtkTexturePainter.cxx, line 173
vtkTexturePainter (0x1a34fd0): Failed to locate selected scalars. Will 
use image scalars by default.


I traced this down to the function:
int vtkTexturePainter::SetupScalars(vtkImageData* input)

which does a

  vtkDataArray* scalars = vtkAbstractMapper::GetScalars(input,
    this->ScalarMode,     this->ScalarArrayName? VTK_GET_ARRAY_BY_NAME : 
VTK_GET_ARRAY_BY_ID,
    this->ScalarArrayIndex,
    this->ScalarArrayName,
    cellFlag);

which becomes NULL. This leads to the above warning. I spent the last 
hours following the information flow in the VTK pipeline and as far as 
my humble understanding goes, all should be fine, because the 
vtkSimpleImageToImageFilter derives from vtkImageAlgorithm which takes 
care that all the OutputPortInformation and all the Requests, etc. are 
setup correctly.

Despite that, Paraview does not seem to have information about the data 
array, at least its not listed where as there IS information on the 
original image: Name:PNGImage DataType: unsigned char, Data Ranges[0,255]...


Here is my SimpleExecution Function:

void vtkDislev::SimpleExecute(vtkImageData* input, vtkImageData*
    output)
    {
      if (input==NULL) {
      vtkErrorMacro(<<"Bad Input to vtkDislev");
      return;
      }
        int dim[3];
      input->GetDimensions(dim);
      int numvox  = dim[0]*dim[1]*dim[2];
      int numcomp = input->GetNumberOfScalarComponents();
        vtkDataArray* inarray  = input->GetPointData()->GetScalars();
      vtkDataArray* outarray = output->GetPointData()->GetScalars();
        unsigned char in=255;
      unsigned char out=0;
      for (int component=0; component < numcomp; component++) {
      for (int i=0; i < numvox; i++) {
          unsigned char v=inarray->GetComponent(i,component);
          if (v >= this->LowerThreshold && v<=this->UpperThreshold) {
          outarray->SetComponent(i,component,in);
          } else {
          outarray->SetComponent(i,component,out);      
      }
      }
      }
}


I would be glad if someone had any idea. Maybe I DO have to rewrite 
these FillOutputInformationVector(...) ?


Best regards,
Christian