[Insight-developers] DifferenceOfGaussiansGradientImageFilter
George Stetten
george@stetten.com
Thu, 23 Jan 2003 13:29:09 -0500
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Jim,
You're right. That would be more accurate name. Thanks.
George
Miller, James V (Research) wrote:
> It really just a "Difference of displaced intensities". There is
> nothing gaussian related to the implementation (internal to this
> filter, you have to feed a smoothed image). I would even avoid the
> idea of difference of displaced gaussians because I infer from that
> name that multiple gaussians are used.
>
>
>
> What is there is basically just a digital derivative where the kernel
> is wider than 3 elements, i.e. instead of using a kernel
>
>
>
> -1, 0, 1
>
>
>
> you are using a kernel
>
>
>
> -1, 0, ..., 0,1
>
>
>
> where there are an odd number of 0's between the -1 and 1.
>
>
>
> I would probably call it something like a
> "WideCentralDifferenceGradientImageFilter".
>
>
>
>
>
> -----Original Message-----
> From: George Stetten [mailto:george@stetten.com]
> Sent: Thursday, January 23, 2003 12:50 PM
> To: Miller, James V (Research)
> Cc: Insight-developers (E-mail)
> Subject: Re: [Insight-developers]
> DifferenceOfGaussiansGradientImageFilter
>
> 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.
>>
>>_______________________________________________
>>Insight-developers mailing list
>>Insight-developers@public.kitware.com
>>http://publ
>>ic.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
>
>
--
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>
You're right. That would be more accurate name. Thanks.<br>
<br>
George<br>
<br>
Miller, James V (Research) wrote:<br>
<blockquote type="cite" cite="mid:FBE90DFC240BA541B38A43F39913A16D04460F89@xmb02crdge">
<meta content="MSHTML 6.00.2715.400" name="GENERATOR">
<div><span class="470150918-23012003"><font color="#0000ff" size="2">It
really just a "Difference of displaced intensities". There is nothing gaussian
related to the implementation (internal to this filter, you have to feed
a smoothed image). I would even avoid the idea of difference of displaced
gaussians because I infer from that name that multiple gaussians are used.</font></span></div>
<div><span class="470150918-23012003"></span> </div>
<div><span class="470150918-23012003"><font color="#0000ff" size="2">What
is there is basically just a digital derivative where the kernel is wider
than 3 elements, i.e. instead of using a kernel</font></span></div>
<div><span class="470150918-23012003"></span> </div>
<div><span class="470150918-23012003"><font color="#0000ff" size="2">-1,
0, 1</font></span></div>
<div><span class="470150918-23012003"></span> </div>
<div><span class="470150918-23012003"><font color="#0000ff" size="2">you
are using a kernel</font></span></div>
<div><span class="470150918-23012003"></span> </div>
<div><span class="470150918-23012003"><font color="#0000ff" size="2">-1,
0, ..., 0,1</font></span></div>
<div><span class="470150918-23012003"></span> </div>
<div><span class="470150918-23012003"><font color="#0000ff" size="2">where
there are an odd number of 0's between the -1 and 1.</font></span></div>
<div><span class="470150918-23012003"></span> </div>
<div><span class="470150918-23012003"><font color="#0000ff" size="2">I
would probably call it something like a "WideCentralDifferenceGradientImageFilter".</font></span></div>
<div><span class="470150918-23012003"></span> </div>
<div><span class="470150918-23012003"></span> </div>
<blockquote style="padding-left: 5px; margin-left: 5px; border-left-width: 2px; border-left-style: solid; border-left-color: rgb(0,0,255); ">
<div class="OutlookMessageHeader" dir="Ltr" align="Left"><font face="Tahoma" size="2">
-----Original Message-----<br>
<b>From:</b> George Stetten [<a class="moz-txt-link-freetext" href="mailto:george@stetten.com">mailto:george@stetten.com</a>]<br>
<b>Sent:</b> Thursday, January 23, 2003 12:50 PM<br>
<b>To:</b> Miller, James V (Research)<br>
<b>Cc:</b> Insight-developers (E-mail)<br>
<b>Subject:</b> Re: [Insight-developers] DifferenceOfGaussiansGradientImageFilter<br>
<br>
</font></div>
Jim<br>
<br>
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. <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 cite="mid:FBE90DFC240BA541B38A43F39913A16D04460F84@xmb02crdge" type="cite">
<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<br>ic.kitware.com/mailman/listinfo/insight-developers</a><br></pre>
</blockquote>
<br>
<pre class="moz-signature" cols="$mailwrapcol">-- <br>George Stetten, M.D., Ph.D.<br>Assistant Professor, Bioengineering, U. Pitt.<br>Research Scientist, Robotics Institute, CMU<br><a class="moz-txt-link-freetext" href="http://www.stetten.com">http://www.stetten.com</a><br><br></pre>
<br>
</blockquote>
</blockquote>
<br>
<pre class="moz-signature" cols="$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>
</pre>
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