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## Re: Zerocrossings in an image

 From: Etienne Grossmann Subject: Re: Zerocrossings in an image Date: Sun, 17 Apr 2005 16:23:47 -0400 User-agent: Mutt/1.4.2.1i

```On Sun, Apr 17, 2005 at 09:25:31PM +0200, Søren Hauberg wrote:
# Thanks, not only for the quick response, but also for the code. It
# appears to be working very well for my needs.

# Can I use your code in a gpl'ed script?

Sure.

# /Søren
#
# Etienne Grossmann wrote:
# >Hth
# >
# >f = 2*kron (randn(4)>0,ones(4))-1
# >
# >z0 = f<0;                 ## Negative
# >[R,C] = size(f);
# >z = zeros(R,C);
# >z(1:R-1,:) |= z0(2:R,:);  ## Grow
# >z(2:R,:) |= z0(1:R-1,:);
# >z(:,1:C-1) |= z0(:,2:C);
# >z(:,2:C) |= z0(:,1:C-1);
# >
# >z &= !z0                  ## "Positive zero-crossings"?
# >
# >
# >
# >On Sun, Apr 17, 2005 at 06:02:02PM +0200, Søren Hauberg wrote:
# ># Hi
# ># Does anybody here know a simple way to find the zerocrossings in an
# ># image in Octave?
# ># I usually do something like this (where f is the image (or 2d function))
# >#
# ># zerocrossings = bwmorph(f>=0, "remove");
# >#
# ># but then I depend on bwmorph which only is octave-forge (which I don't
# ># have at school).
# >#
# ># Any help would be great,
# ># \Søren
# >#
# >#
# >#
# ># -------------------------------------------------------------
# ># Octave is freely available under the terms of the GNU GPL.
# >#
# ># Octave's home on the web:  http://www.octave.org
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# ># -------------------------------------------------------------
# >#
# >

--
Etienne Grossmann ------ http://www.cs.uky.edu/~etienne

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