Newsgroups: sci.image.processing
Path: cantaloupe.srv.cs.cmu.edu!rochester!udel!news.mathworks.com!news.kei.com!wang!news
From: rutie@asp.co.il (Rutie Adar)
Subject: Re: What is this edge detector called? Ref?
Reply-To: rutie@asp.co.il
Organization: ASP Solutions LTD.
Date: Sun, 30 Jul 1995 09:23:38 GMT
Message-ID: <DCIvFF.69u@asp.co.il>
References: <3v6e2t$qgi@agate.berkeley.edu>
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In article <3v6e2t$qgi@agate.berkeley.edu>, amnon@adage.Berkeley.EDU (Amnon Silverstein) writes:
> I used the 'Find Edges' button on Adobe Photoshop as part of a research paper.
> The reviewers all wanted to know what 'Find Edges' did exactly, so I tried
> to find out from Adobe, but no one there could tell me. So I reverse-
> engineered it. It is a convolution of the image with the kernel:
>  1  2  1
>  0  0  0
> -1 -2 -1
> 
> And the kernel
> -1  0  1
> -2  0  2
> -1  0  1
> 
> The final output is the Pythagorean sum of the two convolutions.
> 
> Matlab calls these kernels 'Sobel'. I looked up a 1978 Sobel paper that sounded
> like the closest one, and it didn't describe this method for finding edges.
> I've also looked in a few Image Processing books, and i can not find any
> mention of this algorithm.
> 
> Can you tell me who invented this algorithm and where they described it?
> Thanks for any help!
> -Amnon Silverstein
> 


Hi Amnon,

I found in the Image Processing hand-book by John C. Russ a reference to Sobel's
paper: "Camera models and machine perception" from 1970, in AIM-21, stanford AI Lab, Palo Alto. This reference was given regarding the two masks you discribed.

Please let me know if you find anything there - I'm curious too.
-- 

    Rutie Adar,
    ASP Solutions Ltd.                       Tel: 972-9-986976
    Algorithms Dept. Manager,                Fax: 972-9-986980
    HaTaasiya 9, Raanana 43100, Israel.      E-mail: rutie@asp.co.il


