The CannyEdgeDetectionImageFilter has a SetVariance method. The variance is sigma squared. Are you specifying a variance of 900?<br>
<br>
Bill<br>
<br><br><div><span class="gmail_quote">On 6/25/06, <b class="gmail_sendername">Shlomo Kashani.</b> <<a href="mailto:shlomo_kashani@yahoo.com">shlomo_kashani@yahoo.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><span class="e" id="q_10c0bc21b3e323ce_0"><div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3">Hi All,</font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3">I am trying to use the class
</font><span style="font-size: 10pt;">CannyEdgeDetectionImageFilter </span><font face="Times New Roman" size="3">in
an iris recognition system. One of the first steps is segmenting the
iris and the pupil by and edge detector and then finding the radii of
the pupil and the iris using a circular Hough Transform. I have several
questions regarding the canny edge detector implementation in ITK:</font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3"> </font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3">
1-I
understand that in the original paper by Canny a first derivative of a
Gaussian was used while ITK uses a LoG operator (second derivative of a
Gaussian). Why was this method chosen over the original suggested
method? </font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3"> </font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3">2-in the class </font><span style="font-size: 10pt;">
CannyEdgeDetectionImageFilter</span><font face="Times New Roman" size="3">,
I noticed that there is no way of specifying the SIZE of the Gaussian
kernel that the canny edge detector would use (by a call to </font><span style="font-size: 10pt;">DiscreteGaussianImageFilter I guess ???)</span><font face="Times New Roman" size="3">, rather only the standard deviation can be specified and I understand that the kernel size is determined
automatically from the standard deviation. Is that correct and is there a way to over ride this behavior?</font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3"> </font></div> <div style="margin: 0in 0in 0pt;">
<font face="Times New Roman" size="3">3-I
noticed that when using ITK I have to use a standard deviation as large
as *30* which would probably result in a huge Gaussian and Gaussian
derivative kernel size while when using MATLAB (which uses a first
derivative of a Gaussian) a standard deviation of 5 is enough. How come
there is such a hug difference?</font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3"> </font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3">Any help would be appreciated,
</font></div> <div style="margin: 0in 0in 0pt;"><font face="Times New Roman" size="3"> </font></div> <div style="margin: 0in 0in 0pt;"><font size="3"><font face="Times New Roman">Shlomo Kashani. <span> </span></font></font>
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