[Insight-users] GradientAnisotropicDiffusionImageFilter

[Joshua Cates]

Hi Zein,

A time step of 0.125 should be fine with the Gradient... filter and 3D
data.  (The CurvatureAnisotropicDiffusion... filter is a different story.)
This warning is probably being generated in error.  I'll have a look.

I can't explain why you would get no change in the output.  Rest assured 
these filters are tested nightly and should be working fine.  Note that 
the conductance and number of iterations required for a reasonable result 
will vary widely with the data. 

I suggest you experiment with a small chunk of your data (so that you can 
do iterations quickly) to get appropriate settings for your data.

One more thing: be sure to convert your data to floating point values 
before filter.  This is a pde filter and the algorithm doesn't make sense 
with integer types.

hope this helps,

Josh.


On Mon, 28 Jun 2004, salah wrote:

> Hello all,
> 
> I am trying to perform edge-preserving smoothing by the 
> 
> GradientAnisotropicDiffusionImageFilter
> 
> I used the following parameter values:
> 
> filter->SetNumberOfIterations( 5 );
> filter->SetTimeStep( 0.125 );
> filter->SetConductanceParameter( 3 );
> 
> 1. I got a warning that 0.125 is not a stable value and that the minimum
>    stable values is 0.0625.
> 
> 2. However with both these values and the other parameter values, the 
>    output image is just the same as the input image. I tested this with
>    CT input images of USHORT and UCHAR pixel types.
> 
> What could the problem be ? what are appropriate values to use with this
>    Filter? Does the other edge-preserving smoothing filters differ?
> 
> 
> Many thanks,
> 
> Zein
> 
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