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Re: Filter image with moving window and averaging pixels [message #52434 is a reply to message #52350]

Wed, 31 January 2007 15:52

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Wed, 31 Jan 2007 10:58:39 -0800, rpertaub@gmail.com wrote:

> Hello,
> I need to filter some noise out of an image and was pointed towards
> making a moving/sliding window (size, say 7x7) and compare the center
> pixel with surrounding pixels right next to border (ignoring middle
> pixels). And compare the value of center pixel with the border average
> pixels and thus filter out noise. However, I am not sure how to do
> this.
> Anyone has any idea?
> Did I say I was new to IDL...?
> Thanks for all your help,
> my last query was met by very helpful replies, and I am grateful!

I'd use CONVOL, e.g.:

kernel=fltarr(7,7)
kernel[0,*]=1.
kernel[6,*]=1.
kernel[*,0]=1.
kernel[*,6]=1.

imconv=convol(image,kernel,/CENTER,/EDGE_TRUNCATE)/(4*7-4)
bad=where(abs(image-imconv) gt threshold)

Then again, a box median might be just as good of a statistic, especially
if coupled to a box standard deviation. The former is easy, the latter
requires some SMOOTH trickery, discussed several times here.

JD

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[Message index]

		Filter image with moving window and averaging pixels By: rpertaub@gmail.com on Wed, 31 January 2007 10:58
		Re: Filter image with moving window and averaging pixels By: rpertaub@gmail.com on Thu, 01 February 2007 08:13
		Re: Filter image with moving window and averaging pixels By: JD Smith on Wed, 31 January 2007 15:52
		Re: Filter image with moving window and averaging pixels By: Michael Galloy on Wed, 31 January 2007 15:55

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