[Insight-users] Canny Edge Detection Filter Qns., etc.

[Kalpathi Subramanian]

Kalpathi Subramanian wrote:
> 1. I am wondering about the two hysteresis thresholds (lower and
> upper thresholds) in this filter.
> If I remember this (I implemented all of this in my post-doc BSP tree
> project many, many years back), the thresholds were on the 
> CDF(cumulative distr. fn) of the gradient magnitudes. Is this the case 
> here? Or are the thresholds on
> just the gradient magnitude (maybe my implementation was based on
> another related implementation, I dont quite remember). Anyhow, this
> had the advantage that I could give these thresholds as percentages
> on the CDF..


I stared at the code and it looks like its accepting gradient magnitude
thresholds (to do the hysteresis thresholding), however I am puzzled
as to how to specify the thresholds, as the gradient magnitude filter
is embedded within this filter. Is there a wave to retrieve
the min and max values of the  gradient magnitudes?

Thanks.

	-- krs

> 
> 2.   - on reading raw data. There is a .mhd file needed
> to read raw data. Can someone point me to its format?
> 
> 3. Has anyone read the Colon datasets available from NLM 
> (nova.nlm.nih.gov) - I have tried it with the itkDicomSeriesReader
> but have had problems.. will try again but the images didnt
> seem like the original CT data; instead looked like binary images..
> 
> 
> Thanks.
> 
>     -- krs
> 
> 

-- 
K.R.Subramanian                        Phone: (704) 687-8579
Department of Computer Science         FAX:   (704) 687-3516
UNC Charlotte, STech 435E              Email: krs at uncc.edu
Charlotte, NC 28223-0001               Web: http://www.cs.uncc.edu/~krs