[Insight-developers] RecursiveMultiResolutionPyramidImageFilter

[Bradley Lowekamp]

Hello Sam,

I looked at the images you provided here:

 http://www.cs.utah.edu/~sgerber/tmp/pyramids.zip

in Slicer3D. I would agree that test1 from the RecursivePyramid with the shrink filter does not appear to align up correct. So you are likely onto something.

What I have found useful for many of these types of geometric filters is to create an image of points of the physical location of center of the pixels, or a set of images if the filter in question doesn't support the multi-component pixels. Then pass this through the filter. Aside from potential boundary conditions the the pixel values of the output should still be the physical location of the pixel in the output. This can create useful and definitive tests.

Brad

On Jul 17, 2013, at 11:15 AM, sgerber <sgerber at cs.utah.edu> wrote:

> Hi
> 
> RecursiveMultiResolutionPyramidImageFilter behaves significantly different when using UseShrinkImageFilterOff() vs. UseShrinkImageFilterOn(). The default, UseShrinkImageFilterOn(), uses for subsampling a single pixel ("top right" corner) which results, for piecewise constant images, in image gradients being shifted in physical space. Is this intended? It's not the behaviour I expected when I used this filter. It is also not documented in the PyramidFilter documentation or the ShrinkImageFilter that this is the subsampling method used.
> 
> Thanks
> Sam
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