[Insight-users] about level set

[Luis Ibanez]

Hi Yixun,

If you are concerned about the degree of smoothing
you can simply use a small value for Sigma.

Keep in mind that the concept of "Gradient" in
digital data is inseparable from the notion of
"Scale".  What the smoothing is doing for you is
making sure that you compute Gradients at a
particular Scale.

If you really find that the Gaussian smoothing (even
with small sigmas) is degrading the contours, then
feel free to go for the GadientMagnitude filter that
uses simple finite differences in order to estimate
the gradient. What you see in the Software Guide is
"one way" of doing things, there are certainly many
other equivalent ways of achieving similar results.


Regards,


   Luis



--------------------
Yixun Liu wrote:

> Hi,
>  
> I read the Level Set algorithm in ITKSofewareGuide. To generate a 
> initial Level set the general pipeline is that firstly smooth the image 
> using a edge-preserving smoother and then feed the relult as the input 
> of the GradientMagnitudeRecursiveGaussianImageFilter to get the 
> gradient. I am very confused. Because the 
> GradientMagnitudeRecursiveGaussianImageFilter needs smooth the image. 
> This smooth will destroy the edge information which is preserved by the 
> edge-preserving filter.
>  
>  
> Best regards,
>  
> Yixun LIu
> 
> 
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