[Insight-users] Smoothing Vector Images

[Merrem, Andreas]

Hi,
 
Yes, that was my idea too... unfortunately the discrete Gaussian filter is even 3 times slower than the recursive one.
Anyway, thanks a lot,
 
Andreas
 
 
 

________________________________

Von: Sergio Vera [mailto:sergio.vera at alma3d.com] 
Gesendet: Mittwoch, 16. Juni 2010 17:10
An: Merrem, Andreas
Cc: Bill Lorensen; insight-users at itk.org
Betreff: Re: [Insight-users] Smoothing Vector Images


Hello
Extracted from the itk doxygen documentation: 

As compared to itk::DiscreteGaussianImageFilter <http://www.itk.org/Doxygen318/html/classitk_1_1DiscreteGaussianImageFilter.html> , this filter (RecursiveGaussianImageFilter) tends to be faster for large kernels, and it can take the derivative of the blurred image in one step. 


so if you are using smaller sigmas and hence, smaller Gaussians, DiscreteGaussianImageFilter may result in faster execution time.


And now I'm speculating but my guess is that 1 second to perform 3x256x256x22 convolutions is not dramatically slow (it seems reasonable, as those represents more than 4 millions of convolution operations), but i don't know if it can be done much more faster.





On Wed, Jun 16, 2010 at 3:41 PM, Merrem, Andreas <andreas.merrem at medma.uni-heidelberg.de> wrote:


	Hi Bill and Sergio,
	
	Thank you for your answers.
	
	I tried using nth element adaptors and the VectorIndexSelectionCastImageFilter, but it doesn't make it faster, what takes time is really the smoothing itself (as you already expected).
	
	Yes, I built both the itk library and the application in release mode. Do you think a second is a reasonable amount of time for smoothing 3 image volumes of size 256*256*22?
	
	If anyone knows a smoothing filter that does Gaussian smoothing and works faster than the itk recursive filter (perhaps something in frequency space) that would be a great help.
	
	
	
	
	
	-----Ursprüngliche Nachricht-----
	Von: Bill Lorensen [mailto:bill.lorensen at gmail.com]
	Gesendet: Dienstag, 15. Juni 2010 20:12
	An: Merrem, Andreas
	Cc: Luis Ibanez; insight-users at itk.org
	Betreff: Re: [Insight-users] Smoothing Vector Images
	

	First question: are you building ITK and your app with Release?
	
	On Tue, Jun 15, 2010 at 11:34 AM, Merrem, Andreas <andreas.merrem at medma.uni-heidelberg.de> wrote:
	> Hi Luis, hi everyone,
	>
	> I am trying to smooth 3D image volumes of size 256 * 256 * 22 pixels,
	> in which each pixel contains a 3 dimensional itk::CovariantVector. The
	> vector components should be smoothed independently over the whole
	> volume. My current solution is to first copy the 3 vector components
	> in each pixel into
	> 3 separate images with pixel type float, then use the
	> itk::RecursiveGaussianImageFilter for smoothing on all 3 images, and
	> finally copy the pixel values of the smoothed images back into the
	> covariant vector image.
	>
	> My problem is that this procedure takes about one second. As a part of
	> a registration program, this leads to extremely slow registration
	> (about 10 minutes for one 256*256*22 dicom volume). Is there a way to
	> use less memory by avoiding the copying, or do you know a different,
	> faster technique of applying a Gaussian filter?
	>
	> Thanks a lot,
	>
	> Andreas
	>
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-- 
Sergio Vera

Alma IT Systems
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