[Insight-users] HessianRecursiveGaussianImageFilter

[Luis Ibanez]

Hi Won-Ki,



1) Yes, the effect of the filter should be equivalent
    to applying smoothing, and following it with second
    derivatives.



2) What version of ITK are you using ?


    This problem was pointed out by Andreas Keil in the
    users list on April 2007:

http://public.kitware.com/pipermail/insight-users/2007-April/022019.html

    We entered in the Bug tracker as Bug # 4934
http://public.kitware.com/Bug/bug.php?op=show&bugid=4934

    and committed a fix in the CVS repository on April 27th 2007:
http://www.itk.org/cgi-bin/viewcvs.cgi/Code/BasicFilters/itkHessianRecursiveGaussianImageFilter.txx?root=Insight&sortby=date&r2=1.5&r1=1.4 



    You may want to update your CVS checkout version of ITK.


    Please let us know if you still find any issues with
    the current version.


      Thanks


        Luis



------------------
Won-Ki Jeong wrote:
> Hi all
> 
> I have some questions about the HessianRecursiveGaussianImageFilter.
> 
> Q1. Is this filter (theoretically) same as applying Gaussian smoothing
> and compute derivatives to the input image? For example, let G be a
> Gaussian kernel and I be the input image, then is the filter compute
> (G*I)xx, (G*I)xy, (G*I)xz, (G*I)yy, (G*I)yz, (G*I)zz (subscript means
> partial derivative along that axis)?
> 
> Q2. If so, the implementation is not correct because, for example
> (G*I)xx, the filter applies 1D recursive Gaussian order-1 derivative
> filter twice along x and applies 1D recursive Gaussian filter along y,
> that means along x the Gaussian is applied twice but there is no
> Gaussian for z direction. Can somebody clarify this?
> 
> The implementation is in void GenerateData(void) in
> itkHessianRecursiveGaussianImageFilter.txx.
> 
> Thanks a lot!
> 
> Won-Ki
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