[vtkusers] vtkImageExtractComponents

[Adrian Albert]

Dear All,


could someone explain to me how I can extract a scalar component from a
multicomponent array using vtkImageExtractComponents ?
I have an vtkStructuredPoints with M scalar components defined over the same
grid, and I would like to apply some scaling using vtkShiftScale to only
several of these components. What I am doing right now is:

  double range[2];
  vtkImageExtractComponents *myImgComp = vtkImageExtractComponents::New ();
  myImgComp->AddInput (inputMultivariateField);
  myImgComp->SetComponents (idx);
  myImgComp->Update ();

  myImgComp->GetOutput ()->GetScalarRange (range);
  vtkDataArray *myArray = inputMultivariateField->GetPointData
()->GetScalars ();
//   myArray->GetRange (range, idx);

  cout<<"##Range for field "<<idx<<": ("<<range[0]<<",
"<<range[1]<<")"<<endl;

  vtkImageShiftScale* shifter = vtkImageShiftScale::New();
  shifter->SetShift(-1.0*range[0]);
  shifter->SetScale(255.0/(range[1]-range[0]));
  shifter->SetOutputScalarTypeToUnsignedChar();
  shifter->SetInput (myImgComp->GetOutput ());
  shifter->ReleaseDataFlagOff();
  shifter->Update();

  vtkDataArray *myChangedComp = shifter->GetOutput ()->GetPointData
()->GetScalars ();

  int nrTuples = myChangedComp->GetNumberOfTuples ();
  int nrComp = myArray->GetNumberOfComponents ();
  double tupN[nrComp], tup;

  for (vtkIdType i = 0; i < nrTuples; i++)
    {
      myArray->GetTuple (i, tupN);
      tup = myChangedComp->GetTuple1 (i);
      tupN[idx] = tup;
      myArray->SetTuple (i, tupN);
    }

  inputMultivariateField->GetPointData ()->SetScalars (myArray);

So I'm extracting one component (which vtkImageExtractComponents copies in a
separate vtkImageData object), and then work on the scalars directly. Is
there another simpler way of doing this?

Thanks!
Adrian

-- 
---------------------------------------------------
Adrian Albert
School of Engineering and Science
Jacobs University Bremen
Germany
Tel.: 00494212003258
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