[Insight-developers] bug in itkGradientVectorFlowImageFilter

[Kishore Mosaliganti]

Hi Bill,

I did that. Here is the link:
http://www.itk.org/Bug/view.php?id=9664

Kishore

On Mon, Oct 5, 2009 at 1:01 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> Kishore,
>
> Can you file a bug report and put your changes in the report?
>
> Thanks,
>
> Bill
>
> On Mon, Oct 5, 2009 at 12:50 PM, Kishore Mosaliganti
> <kishoreraom at gmail.com> wrote:
>> Hi,
>>
>> itkGradientVectorFlowImageFilter does not make use of image spacing.
>> It assumes isotropic spacing of 1 in all dimensions. This is a
>> problem. In particular, the ITK implementation uses the definition of
>> 'r' in Equation 17 which will change for anisotropic cases.
>>
>> Also, the CFL condition for estimating the time-step was incorrectly
>> being computed. The original paper, "Snakes, Shapes, and Gradient
>> Vector Flow" shows the equation incorrectly in Equation 18. It is well
>> known that for the diffusion equation, it is (delta_x)^2 and not
>> delta_x in the denominator.
>>
>> I corrected the code locally in my machine. Basically, I had to set
>> the spacing in new images that were allocated and for the
>> LaplacianImageFilter.
>>
>> I am attaching the modified code.
>>
>>
>> Kishore
>>
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>