[vtkusers] PCA on vtkImageData

[Andrew Crozier]

Hi David,

Thanks for the suggestion. I looked at the vtkThreshold filer, however 
it appears to export the boundary of the thresholded volume, whereas I 
require all points inside the volume. Have you any idea of how to 
achieve that?

BW,
Andrew

On 17/11/14 17:16, David Gobbi wrote:
> 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 <mailto: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
>

-- 
------------------------------------------------------------------------
*Andrew Crozier*
andrew.crozier at medunigraz.at

Postdoctoral Researcher
Institute for Biophysics
Medical University of Graz
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