[Insight-developers] DifferenceOfGaussiansGradientImageFilter

Thu, 23 Jan 2003 12:49:33 -0500

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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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>Insight-developers mailing list
>Insight-developers@public.kitware.com
>http://public.kitware.com/mailman/listinfo/insight-developers
>

-- 
George Stetten, M.D., Ph.D.
Assistant Professor, Bioengineering, U. Pitt.
Research Scientist, Robotics Institute, CMU
http://www.stetten.com

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Jim<br>
<br>
Our use of the phrase "Difference of Gaussian" is perhaps unfortunate. &nbsp;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. &nbsp;This is a
"Difference of Gaussian" but not in the traditional sense. &nbsp;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. &nbsp;<br>
<br>
How about we change the name of our "Difference of Gaussian" to "Difference
of Displaced Gaussians" which is more specific?<br>
<br>
George<br>
<br>
Miller, James V (Research) wrote:<br>
<blockquote type="cite" cite="mid:FBE90DFC240BA541B38A43F39913A16D04460F84@xmb02crdge">
  <blockquote type="cite">
    <blockquote type="cite">
      <pre wrap="">3) the calculation does not appear to be a difference of gaussian <br>gradient calculation<br></pre>
      </blockquote>
      <pre wrap="">I'll defer this to George - it's based on his code. As I <br>understand it, <br>this filter approximates a DOG computation when run in tandem <br>with the <br>BinomialBlurImageFilter.<br><br><br></pre>
      </blockquote>
      <pre wrap=""><!----><br>So there are lots of issues with this filter's name then.  At best it computes a gradient of the<br>image.  However, it is not doing a difference of Gaussians approach internally to the filter.  If you<br>have to pass it a blurred image, then it is merely doing a gradient calculation.  Now if I am feeding<br>with a BinomialBlur, then I am not really doing a difference of Gaussians either.<br><br><br>I would say if you can use another gradient calculator in the system, then use that.  I do think it<br>would be nice to have a DifferenceOfGaussians filter.  It should take a single intensity image and<br>two sigmas.<br><br>_______________________________________________<br>Insight-developers mailing list<br><a class="moz-txt-link-abbreviated" href="mailto:Insight-developers@public.kitware.com">Insight-developers@public.kitware.com</a><br><a class="moz-txt-link-freetext" href="http://public.kitware.com/mailman/listinfo/insight-developers">http://publ
ic.kitware.com/mailman/listinfo/insight-developers</a><br></pre>
      </blockquote>
      <br>
      <pre class="moz-signature" cols="$mailwrapcol">-- 
George Stetten, M.D., Ph.D.
Assistant Professor, Bioengineering, U. Pitt.
Research Scientist, Robotics Institute, CMU
<a class="moz-txt-link-freetext" href="http://www.stetten.com">http://www.stetten.com</a>

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