[Insight-users] Re: 2D Curves Extrator Application

[Luis Ibanez]

Hi Buu,

I assume that you are interested in the GaussianFilter
used in the Curve2D extraction example.

If this is the case, this gaussian filters uses the
RecursiveGaussianImageFilter class.  Inside this class
the gaussian filtering is implemented by approximating
the convolution of a gaussian with an IIR filter.

The coefficients that are computed inside the
RecursiveGaussianImageFilter are the coefficients of
this IIR.

Details about the computation of coefficients can be
found in


  R.Deriche in IEEE-PAMI
  Vol.12, No.1, January 1990, pp 78-87.


You can also find a report online at the INRIA web site:

      http://www.inria.fr/

The title of the report is :

RR-1893 - "Recursively implementating the Gaussian and
its derivatives" by Rachid Deriche.

The PDF and Postscript version can be downloaded from

       http://www.inria.fr/rrrt/rr-1893.html


Note that by selecting the coefficients it is possible
to apply Gaussian Smoothing and the equivalent of convolution
with first and second derivatives of a Gaussian.



If you just want to apply the GaussianFilter and/or its
derivatives you don't have to deal with the computation
of coefficients. It is enough to set the Sigma of the
gaussian with the SetSigma() method.




Please let us know if you have further questions.


Thanks


    Luis


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Buu Tien Phan wrote:

> Dear Dr. Ibanez,
> 
>  
> 
> Thank you for all your help. Now I am working with project related to 2D 
> Curves Extrator Application.
> 
> It is very difficult to see how the Gaussian filter is built and how to 
> compute eigenvectors. Could you
> 
> show me how to compute the filter coefficients. Thank you so much for 
> your time.
> 
>  
> 
>  
> 
> Buu Phan
>