RE: [R] 2D fft DC shift

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From: M. Edward Borasky (znmeb@aracnet.com)
Date: Tue 25 Sep 2001 - 12:42:23 EST 

Message-id: <HBEHIIBBKKNOBLMPKCBBIEANDNAA.znmeb@aracnet.com>

The simplest way to get the "hot spot" in the middle is to pre-multiply the
2D FFT *input* pointwise by a checkerboard pattern of -1s and +1s. For
example, if your input is

a b c d
e f g h
i j k l
m n o p

you would submit

-a b -c d
e -f g -h
-i j -k l
m -n o -p

as input to your 2D FFT. This is from memory; someone with access to an
image processing textbook please correct me if I'm wrong!!! 

--
M. Edward (Ed) Borasky, Chief Scientist, Borasky Research
http://www.borasky-research.net  http://www.aracnet.com/~znmeb
mailto:znmeb@borasky-research.net mailto:znmeb@aracnet.com

If there's nothing to astrology, how come so many famous men were born on
holidays?

> -----Original Message-----
> Date: Sun, 23 Sep 2001 20:04:06 -0700 (PDT)
> From: bradley love <bradley_c_love@yahoo.com>
> Subject: [R] 2D fft DC shift
>
> Hi Everyone,
>
> Does anyone know how to take the output of a 2D fft()
> and shift the DC component to the center?  Is there a
> function that does that?
>
> if you know, please send me an email.
>
> thanks for any help!
>
> brad

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