[vtkusers] vtkImageResample interpolation

[Bruno Travençolo]

Hi, All,

I have some doubt about "vtkImageResample". Why the linear interpolation 
doesn't work with float numbers. Look these examples:

My volume:
0 255 0

After vtkImageResample with Magnification Factor = 5  on 'x' axis:
0 51 102 153 204 255 204 153 102 51 0

It's OK. But if my volume is composed by a number with decimals (1.1), 
like this:

0 1.1 0

After the interpolation I get:
0 0 0 1 1 1 1 1 0 0 0

All the interpolated number are equal to 1. I  expected that the result 
would be an linear interpolation between 0 and 1.1.
Does anyone know why it isn't?

My test code:

   vtkDoubleArray *points = vtkDoubleArray::New();
  points->SetNumberOfTuples(3);
  points->SetTuple1(0,0);
//  points->SetTuple1(1,255);
  points->SetTuple1(1,1.1);
  points->SetTuple1(2,0);

  vtkImageData *vol = vtkImageData::New();
  vol->SetDimensions(3,1,1);
  vol->GetPointData()->SetScalars(points);
  vol->Update();

  double factor[3];
  factor[0] = 5;
  factor[1] = 1;
  factor[2] = 1;
  int InterpolationMode = VTK_RESLICE_LINEAR;

  vtkImageResample *resample = vtkImageResample::New();
  resample->SetInput(vol);
  resample->SetAxisMagnificationFactor(0,factor[0]);
  resample->SetAxisMagnificationFactor(1,factor[1]);
  resample->SetAxisMagnificationFactor(2,factor[2]);
  resample->SetInterpolationMode(InterpolationMode);
  resample->Update();

  vtkStructuredPointsWriter *write = vtkStructuredPointsWriter::New();
  write->SetInput(resample->GetOutput());
  write->SetFileName("teste.vtk");
  write->Write();

thanks,
Bruno.