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Re: Variance in sub-sections? [message #29385 is a reply to message #29383]

Mon, 18 February 2002 06:04

Jaco van Gorkom
Messages: 97
Registered: November 2000

Member

"Joshua Nipper" <nipperjc@ufl.edu> wrote in message
news:a4jph3$qdi$1@spnode25.nerdc.ufl.edu...
> I have a 512x512 image, and I would like to calculate the mean/variance in
a
> 3x3 neighborhood around every pixel. What would be the easiest way to do
> this w/out for loops?

Martin Downing once posted a nifty routine IMAGE_VARIANCE to the group.
Look up a thread called "efficient kernel or masking algorithm ? UPDATE"
on Google.
http://groups.google.com/groups?hl=en&q=variance+kernel& amp;meta=group%3Dcomp.la
ng.idl-pvwave

Things should then be as simple as
variance = IMAGE_VARIANCE(image, 1, MEAN=mean) .

Jaco

PS: I posted without thinking too much on Friday, in response to your
Kuwahara filter post. The variance I suggested was calculated with respect
to a 'sliding' mean value, and probably not a very good choice for this
kuwahara thingie.

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[Message index]

		Re: Variance in sub-sections? By: Joshua Nipper on Mon, 18 February 2002 13:04
		Re: Variance in sub-sections? By: David Fanning on Mon, 18 February 2002 10:31
		Re: Variance in sub-sections? By: Jaco van Gorkom on Mon, 18 February 2002 10:12
		Re: Variance in sub-sections? By: David Fanning on Mon, 18 February 2002 08:42
		Re: Variance in sub-sections? By: Alex Schuster on Mon, 18 February 2002 07:41
		Re: Variance in sub-sections? By: Jaco van Gorkom on Mon, 18 February 2002 06:04

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