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Re: image subtraction [message #29782 is a reply to message #11675]

Wed, 13 March 2002 16:21

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

aburden@mpl.ucsd.edu (Art) writes:
> Hi,
>
> Can anyone come up with an efficient way to subtract a single image
> from an array of images without using a loop, as in
>
> imgArr = imgArr - img1
>
> where,
>
> imgArr = lonarr(12,512,512)
>
> and,
>
> img1 = lonarr(512,512)
>
> as opposed to
>
> For ii=0,11 do imgArr[ii,*,*] = imgArr[ii,*,*] - img1

(a) You can do this:
imgarr = imgarr - rebin(reform(img1,1,512,512),12,512,512)

This makes IMG1 into a 1x512x512 array, and then uses REBIN to
expand it to the desired size.

(b) I don't think a FOR loop will be that much slower than the REBIN
approach, at least for 512x512 arrays.

Good luck,
Craig

--
------------------------------------------------------------ --------------
Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Image subtraction By: FRANCOIS LAROSE on Mon, 18 May 1998 00:00
		Re: Image subtraction By: noname on Tue, 26 May 1998 00:00
		Re: image subtraction By: Dick Jackson on Mon, 18 March 2002 21:45
		Re: image subtraction By: K. Bowman on Sun, 17 March 2002 08:11
		Re: image subtraction By: Dick Jackson on Thu, 14 March 2002 08:00
		Re: image subtraction By: Kenneth P. Bowman on Thu, 14 March 2002 04:55
		Re: image subtraction By: Dick Jackson on Wed, 13 March 2002 18:48
		Re: image subtraction By: Craig Markwardt on Wed, 13 March 2002 16:21

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