[Insight-developers] itkGradientVectorFlowImageFilter

[Lorensen, William E (Research)]

Ting,

First of all this is a great filter to have in itk. Thanks for implementing it.

Some things to consider while you are fixing this filter. I'm assuming you are implementing the
algorithm in:

Xu and Prince, "Snakes, Shapes and Gradient Flow,", IEEE Trans on Image Processing, vol 7, no 3, pp.
359-369.

1) All ivars should have some sort of intelligent default defined in the constructor. This should
include TimeStep, Steps and NoiseLevel. I also suggest that you create a Laplacian in the
constructor. You could still allow the user to overide the Laplacian, except I'm not sure under what
conditions a user would do that.

2) All ivars should have a Get method.

3) The class should have a PrintSelf method.

4) The code is a little hard to follow as far as the naming of interators. For example, intIt and
interIt might be called internalIt and intermediateIt, assuming you retain the names of the Internal
and Intermdiate images.

5) Eqn 18 in the paper has a restriction on the TimeStep. I'm not sure if you are detecting a
violation of the convergence criteria.

6) The computation of r in eqn 17 does not seem to correspond to your implementation.

7) The authors state that b, c1 and c2 can be computed once and fixed for the entire process.

8) The implementation has the number of iterations fixed at 100. Why not make thjis an ivar and set
the defauklt to 100.

Bill




-----Original Message-----
From: Ting Chen [mailto:chenting@graphics.cis.upenn.edu]
Sent: Monday, April 15, 2002 8:22 PM
To: Lorensen, William E (Research)
Cc: insight-developers@public.kitware.com
Subject: Re: [Insight-developers] itkGradientVectorFlowImageFilter


Bill, I will fix it ASAP. Sorry for the problem.

ting


-----Original Message-----
From: Lorensen, William E (Research) <lorensen@crd.ge.com>
To: Lorensen, William E (Research) <lorensen@crd.ge.com>; 'Ting Chen'
<chenting@graphics.cis.upenn.edu>
Cc: insight-developers@public.kitware.com
<insight-developers@public.kitware.com>
Date: Monday, April 15, 2002 2:32 PM
Subject: RE: [Insight-developers] itkGradientVectorFlowImageFilter


>Ting,
>Also, this filter has no documentation...
>
>-----Original Message-----
>From: Lorensen, William E (Research)
>Sent: Monday, April 15, 2002 9:14 AM
>To: 'Ting Chen'
>Cc: insight-developers@public.kitware.com
>Subject: [Insight-developers] itkGradientVectorFlowImageFilter
>
>
>Ting,
> A user is reporting that the subject filter is not compiling. I noticed
that there are not
>tests for this filter. Could you look into this?
>
>Bill
>
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