[Insight-users] Question about Levelset

[Luis Ibanez]

Hi Yohan,


Unless you really want to reimplement the LevelSet framwork of ITK,
you may find more useful to simply add your partial differential
equation to the existing ITK framework and let ITK do for you all
the dirty job of computing derivatives, curvatures, and distances.


All those functionalities are already available in the LevelSet
framework. You simply need to define new LevelSet functions that
specify how to compute the speed image of the level set.


For examples on how to implement new LevelSet methods, you may want
ot study the code of the ShapeDetectionLevelSet.


Notice that you will find

           1) ShapeDetectionLevelSetFunction

and

           2) ShapeDetectionLevelSetImageFilter

both in the directory


           Insight/Code/Algorithms



You should also study the superclasses:


            1) SegmentationLevelSetFunction

and

            2) SegmentationLevelSetImageFilter



You must read the "Level Set" chapter in the ITK Software Guide


     http://www.itk.org/ItkSoftwareGuide.pdf



   Regards,


      Luis



=================================
m26402022 at john.petra.ac.id wrote:
> 
> Hello,
> 
>    My name is Yohan. I need some assisstance in Levelset.
> 
>   I've made an application using levelset method. based on the paper I've found
> on website there are three things I want to ask:
> 
>  1. Distance (z = d(x,y,t=0))
> 
>     All I know z is the distance of a point(x,y) to our initial curvature in
>     Normal direction.
>     So I make it this way, I have 10x10 image plain and I made a circle as an
>     initial curve. The result is:
> 
>     3  2  2  2  2  2  3  3  4  5
>     2  1  1  1  1  1  2  3  3  4   is this is what the distance means(z)??
>     1  1  0  0  0  1  1  2  3  4
>     1  0 -1 -1 -1  0  1  1  2  3   0 values are the initial curvature (circle)
>     0 -1 -2 -2 -2 -1  0  1  2  3   + values are the point outside init. circle
>     0 -1 -2 -3 -2 -1  0  1  2  3   - values are the point inside init. circle
>     0 -1 -2 -2 -2 -1  0  1  2  3
>     1  0 -1 -1 -1  0  1  1  2  3
>     1  1  0  0  0  1  1  2  3  4
>     2  1  1  1  1  1  2  3  3  4
> 
>  2. Speed function F(K)=F + F (k)=(1-eK)
>                          0   1
> 
>     K is the curvature and all I know is :
> 
>               2                       2
>         dxx dy - 2 dx dy dxy + dyy dx           Note : d  is the distance
>     K = -----------------------------------    xx means second derivative to x
>                      2    2  3/2
>                   (dx + dy  )
> 
>     I want to ask about derivative, what is the correct way to calculate first
> derivative
>     and second derivative, can I use sobel??
> 
>                                                       2    2  3/2
>     Also about the divider from equation k wich is (dx + dy  )    . if i use
> sobel there are
>     some condition where the result is a zero. so the equation cannot be done
> because the divider
>     is zero. what should I do with it??
> 
> 
> Regards,
> 
> 
> Yohan
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