[Insight-users] Threaded Gaussian Filter

[Karthik Krishnan]

Obviously, when you manually iterate over every pixel like that :

  it.GoToBegin();
  out.GoToBegin();
  while (!it.IsAtEnd()) {
      out.Set( gaussianFunction->EvaluateAtIndex(it.GetIndex() ) );
      ++it;
      ++out;
  }

its not going to magically multithread itself :)


Either use the neighborhoodoperatorImageFilter, which is threaded....

Or better still, why don't you use the DiscreteGaussianImageFilter/
RecursiveGaussianImageFilter ?

Convolving with a gaussian is the same as smoothing with it, since the
gaussian function is symmetric.



On Thu, Oct 1, 2009 at 4:48 PM, Mike Jackson
<mike.jackson at bluequartz.net> wrote:
> After reading the documentation for each class what is the definition
> of "large" kernel? My image is 3000 x 3000 Pixels and the kernel we
> are wanting to use is 25 pixels with a Sigma of 3 pixels.
>
> Thanks
> _________________________________________________________
> Mike Jackson                  mike.jackson at bluequartz.net
>
>
> On Thu, Oct 1, 2009 at 3:59 PM, Karthik Krishnan
> <karthik.krishnan at kitware.com> wrote:
>> Which gaussian smoothing / convolution filter are you using ?
>> itk::DiscreteGaussianImageFilter or itk::RecursiveGaussianImageFilter.
>>
>> In any case, both are threaded. However the execution time differs
>> based on the filter you use.
>>
>> The first is slower, uses a neighborhood operator and visits each
>> pixel with a gaussian kernel. Its speed will depend on the
>> MaximumKernelWidth parameter given to the filter.
>>
>> The second is an IIR filter, however its much faster for a large
>> image, its implemented using a separable kernel and is based on
>> Deriche's approximation. (Its not based on a pixel wise neighborhood
>> convolution operation).
>>
>>
>>
>> On Thu, Oct 1, 2009 at 1:41 PM, Mike Jackson
>> <mike.jackson at bluequartz.net> wrote:
>>> Anyone have a threaded version of the Gaussian Filter? I am currently
>>> using the example code for a Gaussian filter from the ITK distribution
>>> and for the image size I am throwing at it, the iteration loop takes a
>>> long time because it performs the filter serially on every pixel.
>>>
>>> Thanks
>>> _________________________________________________________
>>> Mike Jackson                  mike.jackson at bluequartz.net
>>> BlueQuartz Software                    www.bluequartz.net
>>> Principal Software Engineer                  Dayton, Ohio
>>> _____________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
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>>>
>>> Please keep messages on-topic and check the ITK FAQ at: http://www.itk.org/Wiki/ITK_FAQ
>>>
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>>>
>>
>>
>>
>> --
>> Karthik Krishnan
>> R&D Engineer,
>> Kitware Inc.
>> Ph: 518 881 4919
>> Fax: 518 371 4573
>>
> _____________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the ITK FAQ at: http://www.itk.org/Wiki/ITK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.itk.org/mailman/listinfo/insight-users
>



-- 
Karthik Krishnan
R&D Engineer,
Kitware Inc.
Ph: 518 881 4919
Fax: 518 371 4573