[Insight-developers] DifferenceOfGaussiansGradientImageFilter

[Stephen R. Aylward]

This is officially called difference of offset Gaussians - DooG.   It is 
fairly standard.   For zoom invariance, the distance of the offset 
should be proportional to the scale of the Gaussians...

s

George Stetten wrote:
> Jim
> 
> Our use of the phrase "Difference of Gaussian" is perhaps unfortunate. 
>  We blur the image with a recurrent binormial filter that approximates a 
> Gaussian, and then produce the components of the gradient by subtracting 
> the intensity at two points displaced along each of the cardinal 
> directions.  This is a "Difference of Gaussian" but not in the 
> traditional sense.  The traditional DOG is two concentric Gaussians of 
> different scale, yielding something approximating a Laplacian, which 
> yields zero-crossings at the boundaries independent of orientation.  
> 
> How about we change the name of our "Difference of Gaussian" to 
> "Difference of Displaced Gaussians" which is more specific?
> 
> George
> 
> Miller, James V (Research) wrote:
> 
>>>>3) the calculation does not appear to be a difference of gaussian 
>>>>gradient calculation
>>>>
>>>I'll defer this to George - it's based on his code. As I 
>>>understand it, 
>>>this filter approximates a DOG computation when run in tandem 
>>>with the 
>>>BinomialBlurImageFilter.
>>>
>>>
>>
>>So there are lots of issues with this filter's name then.  At best it computes a gradient of the
>>image.  However, it is not doing a difference of Gaussians approach internally to the filter.  If you
>>have to pass it a blurred image, then it is merely doing a gradient calculation.  Now if I am feeding
>>with a BinomialBlur, then I am not really doing a difference of Gaussians either.
>>
>>
>>I would say if you can use another gradient calculator in the system, then use that.  I do think it
>>would be nice to have a DifferenceOfGaussians filter.  It should take a single intensity image and
>>two sigmas.
>>
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> 
> -- 
> George Stetten, M.D., Ph.D.
> Assistant Professor, Bioengineering, U. Pitt.
> Research Scientist, Robotics Institute, CMU
> http://www.stetten.com
> 
> 


-- 
===============================================
Dr. Stephen R. Aylward
Assistant Professor of Radiology
Adjunct Assistant Professor of Computer Science
http://caddlab.rad.unc.edu
aylward@unc.edu
(919) 966-9695