[Insight-users] Difference between DiscreteGaussianImageFilter & RecursiveGaussianImageFilter?

[Luis Ibanez]

Hi Parag,

Your question make us notice that there was no
example illustrating the use of the RecursiveGaussian
for blurring images.

One example was just added. It is under

Insight/Examples/Filtering

    SmoothingRecursiveGaussianImageFilter.cxx

This is one of the examples that maps into the
documentation of the SoftwareGuide. So, a
corresponding section will appear in the next
release of the PDF document.

You can run this example in the command line
in order to compare it with the DiscreteGaussian.


Please let us know if you find any problems,


Thanks


   Luis


-------------------------------

Luis Ibanez wrote:

> 
> Hi Parag,
> 
> The basic difference between these two filters is that
> DiscreteGaussian applies a convolution with a gaussian
> kernel while RecursiveGaussian approximates this convolution
> with IIR filters.
> 
> RecursiveGaussian has the drawback of being implemented
> as a basic component for building up other filters.
> It is applied along a single dimension (out of the ND).
> So, in practice you may have to enchain N of these filters
> in order to smooth an ND image.  In that sense, the
> DiscreteGaussian is more convenient to use.
> 
> We may want to implement a variant of the RecursiveGaussian
> that encapsulates the elements necessary to smooth an image
> along all the dimensions. It shouldn't be too complicated
> to implement.
> 
> If you are considering large sigmas, you are probably better
> with the RecursiveGaussian filter since its number of
> computations is independent of the sigma value.
> 
> 
> ---
> 
> The SoftwareGuide.pdf have a discussion on smoothing filters.
> Please take a look at section 5.5. You will find the classical
> gaussian convolutions in section  5.5.1 and the edge-preserving
> smoothing filters in section 5.5.2.
> 
> There is a minimal examples that you can run in the command
> line under:
> 
> Insight/Examples/Filtering:
> 
> - DiscreteGaussianImageFilter.cxx
> 
> you can feed it with Meta, PNG or DICOM images.
> 
> The GaussianFilter and GaussianFilter2D demo-application
> use the RecursiveGaussian filters, so you can get a feeling
> of its performance.
> 
> 
>  Please let us know if you have further questions
> 
> 
>   Thanks
> 
> 
>    Luis
> 
> 
> 
> ------------------------------------------------------------------
> 
>  Chandra wrote:
> 
>> I have a 2-D image that I want to blur using a Gaussian, and I know 
>> the value of sigma for the Gaussian I should use. Which of these two 
>> filters is best for that purpose? If both are suitable, I would like 
>> to know which one will result in a smoother image.
>>
>>  
>>
>> Thanks,
>>
>> Parag Chandra
>>
> 
> 
> 
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