VISION-LIST Digest 1988 10 13

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· 10 months ago

Vision-List Digest	Thu Oct 13 18:11:26 PDT 1988 

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Today's Topics: 

 Circle Detection 
 Need info on uses of Gabor Transform 

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Date: Tue, 11 Oct 88 08:34:18 -0400 
Subject: Circle Detection 
From: "Kenneth I. Laws" <klaws@note.nsf.gov> 

 
Another approach to circle detection is to compute circle centers from 
pairs of edge vectors, then use cluster analysis.  This maintains 
floating-point resolution without the overhead of a large Hough 
accumulator, but may require multiple passes through the database of 
hypothesized circle centers.  It's best to use only edge vectors at 
approximate right angles, and to discard any pairs for which one edge 
vector is further from the computed center than is the other. 

I wrote a paper on this while I was at USC, back about 1977. 
My papers are still in moving boxes, so I don't have this and 
other citations handy.  There have been a number of circle or 
ellipse finders based on Hough methods.  Some of the new neural 
network approaches (such as adaptive resonance) could also be 
used -- they're mostly just template matching, but the more 
complex models can handle distortion and perhaps occlusion. 

For work that depends on local continuity and gestalt grouping, 
you might look into the work of Deborah Walters and her students 
at SUNY.  They might not be able to recognize circles, but they 
can pull out closed (or even open) curves.  Another source of 
ideas is the engineering literature on finding curves in 
handwriting and hand-drawn circuit diagrams or flowcharts. 

					-- Ken Laws 

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Date: 12 Oct 88 01:33:07 GMT 
From: efrethei@BLACKBIRD.AFIT.AF.MIL (Erik J. Fretheim) 
Subject: Need info on uses of Gabor Transforms 
Organization: Air Force Institute of Technology; WPAFB, OH 

 
Has anyone seen the Gabor transform used for anything other than 
edge/texture detection or data compression?  If you know of any other 
interesting applications please let me know. 

   Thank you for your time 
	ejf 

	[ Gabor functions have also been used for low-level motion/energy 
	  detection.  Some references are Adelson and Bergen, J. Opt. 
	  Soc. Amer. A, V2, N2, 2/85; Heeger, IEEE Proc. Intern. Conf. 
	  Comp. Vision (ICCV), 6/87; Fleet and Jepson, Comput. Intell., 
	  V1, 1985.  The original paper by Gabor (who received the Nobel 
	  prize for his work in holography) is "Theory of Communication," 
	  J. Inst. Electr. Eng., V93, 1946.  
			phil... 	] 

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