[vtkusers] PCA on vtkImageData

[David Gobbi]

Hi Andrew,

The vtkThreshold filter will extract only the cells with the desired
scalar values, and will output them as an unstructured grid.  It
isn't exactly what you want because it extracts cells, rather than
points, but it might be worth a shot.

 - David

On Mon, Nov 17, 2014 at 8:28 AM, Andrew Crozier <
andrew.crozier at medunigraz.at> wrote:

> Hi,
>
> I am trying to evaluate the principal components of a strucutre in a 3D
> volume image, to determine its spatial alignment for use in an automatic
> processing pipeline.
>
> The input is a vtkImageData, with multiple integer values (say, 0, 1, 2
> and 3), and I want to perform PCA on the positions of all voxels with value
> 2, for example.
>
> I have looked at vtkPCAAnalysisFilter, and this requires an input of
> vtkPointSet. vtkImageDataToPointSet converts a vtkImageData to a
> vtkStructuredGrid, however I expect this to include all points in the
> original image. At the moment I seem to be missing some way of filtering
> out the points other than those of value 2.
>
> Any help provided for this would be greatly appreciated!
>
> Best wishes,
> Andrew Crozier
>
>
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