[vtkusers] About vtkImageReslice interpolation

[Simon ESNEAULT]

Hi All,

We use vtkImageResample/vtkImageReslice (from vtk 5.8.1) quite a lot here,
and I've noticed a strange behavior.

If we down sample a volume by a factor of 2 in all 3 directions, the output
image will be the exact same if we use a nearest neighborhood, linear or
cubic interpolation. There seems to be no interpolation at all if the
reduction factor is a power of two.
If the reduction factor is set to 2.00001, the interpolation is performed
correctly when asked for linear or cubic.

Is this an intended behavior ?

After some debugging :
In the file vtkImageReslice.cxx, method vtkTricubicInterpCoeffs (line 1503)
 with a power of 2 factor we always fall back to the part with the comment
// no interpolation (line 1510), but I don't understand why.

And last question : there is a new vtkImageResize that was introduced in
vtk 5.10, will the behavior be the same ?

Thanks for your help

-Simon


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Simon Esneault
13 rue Vasselot
35000 Rennes, France
Tel : 06 64 61 30 94
Mail : simon.esneault at gmail.com
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