[Insight-developers] Gaussian filter performance

[Mark Foskey]

Yes, I had noticed the same thing but I hadn't yet followed up.  I 
wasn't as systematic as you were, so I wasn't as confident of my 
results.  This means that the documentation I recently put in the 
comments may be false, as they advocate using the discrete gaussian 
filter for a small kernel.

I also noticed, however, that the result of applying the discrete 
gaussian filter to a binary image looked more like my idea of a 
smoothed image than did the recursive gaussian.  So I'm also interested 
in knowing if there is wisdom out there on the accuracies of both methods.

If it turns out that we can't say that the discrete gaussian is more 
accurate, it is questionable whether we should keep it.

Paul Yushkevich wrote:
> I have been trying to choose an appropriate Gaussian blurring filter to 
> use in the SnAP project.  While doing so, I tried to compare the 
> performance of three candidates from ITK and VTK on a sample image.  The 
> candidates were itk::DiscreteGaussianImageFilter, 
> itk::RecursiveGaussianImageFilter and vtkImageGaussianSmooth .  I ran 
> the filters with default parameters, only changing the standard deviation.
> 
> Perhaps the result is useful to others, so I post it here.  For one 
> thing, it shows that the recursive gaussian filter seems to perform 
> better on even very small sigmas.  What is the error of the recursive 
> filter w.r.t to the true solution for subpixel values of sigma?
> 
> The times listed below are for VC6 Release program running on a 
> two-month old machine.
> 
> Loaded image     : image01.mha
> Image size       : 7109137 bytes
> Image dimensions : 181 x 217 x 181
> Component count  : 1
> File type        : Binary
> File byte order  : Little Endian
> 
> Standard Deviation: 0.5
>   ITK Discrete Gaussian   : 3688ms.
>   ITK Recursive Gaussian  : 515ms.
>   VTK Gaussian            : 1907ms.
> 
> Standard Deviation: 1.5
>   ITK Discrete Gaussian   : 4578ms.
>   ITK Recursive Gaussian  : 484ms.
>   VTK Gaussian            : 2281ms.
> 
> Standard Deviation: 2.5
>   ITK Discrete Gaussian   : 5672ms.
>   ITK Recursive Gaussian  : 485ms.
>   VTK Gaussian            : 2406ms.
> 
> Standard Deviation: 3.5
>   ITK Discrete Gaussian   : 7079ms.
>   ITK Recursive Gaussian  : 500ms.
>   VTK Gaussian            : 2781ms.
> 
> Standard Deviation: 4.5
>   ITK Discrete Gaussian   : 8578ms.
>   ITK Recursive Gaussian  : 484ms.
>   VTK Gaussian            : 3078ms.
> 
> Paul.
> 
> 
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-- 
Mark Foskey    (919) 843-5436  Computer-Aided Diagnosis and Display Lab
mark_foskey@unc.edu            Department of Radiology, CB 7515, UNC
http://www.cs.unc.edu/~foskey  Chapel Hill, NC  27599-7515