[Insight-users] Problems with bilateral filtering

[Bill Lorensen]

Yes, boundary checking slows it down.

On Tue, Jun 22, 2010 at 3:18 PM, Stuart Golodetz <itk at gxstudios.net> wrote:
> Stuart Golodetz wrote:
>>
>> Hi,
>>
>> I think I may be having some trouble using BilateralImageFilter
>> appropriately and just thought I should check. Essentially, I'm trying it
>> out as a replacement to multiple iterations of anisotropic diffusion
>> filtering for edge-preserving smoothing of my input image, using the
>> following code:
>>
>> ###
>> ...
>> typedef itk::BilateralImageFilter<RealImage,RealImage> BilateralFilter;
>> BilateralFilter::Pointer bilateralFilter = BilateralFilter::New();
>> bilateralFilter->SetInput(realImage);
>> double domainSigmas[] = {6.0,6.0,6.0};   // test values (not connected to
>> the GUI yet)
>> double rangeSigma = 5.0;   // ditto
>> bilateralFilter->SetDomainSigma(domainSigmas);
>> bilateralFilter->SetRangeSigma(rangeSigma);
>> bilateralFilter->Update();
>> realImage = bilateralFilter->GetOutput();
>>
>> if(is_aborted()) return;
>> increment_progress();
>> ...
>> ###
>>
>> I was hoping it was going to be faster than the anisotropic filtering I'm
>> currently doing, as that takes about a second per iteration per 512x512
>> slice (i.e. 30 seconds per slice for 30 iterations, which is not ideal):
>>
>> ###
>> ...
>> // Smooth this real image using anisotropic diffusion filtering.
>> typedef itk::GradientAnisotropicDiffusionImageFilter<RealImage,RealImage>
>> ADFilter;
>> for(int i=0; i<m_segmentationOptions.adfIterations; ++i)
>> {
>>   ADFilter::Pointer adFilter = ADFilter::New();
>>   adFilter->SetInput(realImage);
>>   adFilter->SetConductanceParameter(1.0);   // test value (not connected
>> to the GUI yet)
>>   adFilter->SetNumberOfIterations(1);   // done this way so that I can
>> update the progress after each iteration
>>   adFilter->SetTimeStep(0.0625);
>>   adFilter->Update();
>>   realImage = adFilter->GetOutput();
>>
>>   if(is_aborted()) return;
>>   increment_progress();
>> }
>> ...
>> ###
>>
>> Unfortunately, it takes 3 minutes for a 512x512 slice, whilst producing
>> "worse" results (in my context) than the anisotropic diffusion filtering I
>> was doing before. So I have three questions:
>>
>> 1) Would you expect bilateral image filtering to take this long? If not,
>> do you have any idea what I might be doing wrong please? (If not, is there
>> anything I can investigate to try and track down the problem myself?)
>> 2) Are the domain and range parameters having any effect on this, and how
>> should I go about setting them appropriately please?
>> 3) Am I barking up the wrong tree by trying to use bilateral image
>> filtering as a drop-in alternative to anisotropic diffusion filtering like
>> this?
>>
>> Cheers,
>> Stu
>
> A separate (but related) question I have is: why would 3D anisotropic
> diffusion filtering on a 512x512x1 volume be substantially slower than 2D
> anisotropic diffusion filtering on a 512x512 slice? I know the time step has
> to be smaller for the 3D version, but I recall it still being substantially
> slower than before. However, 3D anisotropic diffusion filtering on a larger
> volume e.g. 512x512x20 wasn't all that slow considering what it was doing. I
> was wondering whether boundary checking might be slowing it down? Or is
> there actually some other reason I haven't thought of?
>
> Cheers,
> Stu
> _____________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Kitware offers ITK Training Courses, for more information visit:
> http://www.kitware.com/products/protraining.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
>