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Re: finding the center of gravity of an irregularly shaped roi within a 2d array [message #81257 is a reply to message #81256]

Mon, 03 September 2012 09:24

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

ian.j.ashpole@googlemail.com writes:

> If i can ask, as i am unable to find this in the code as a relative novice, how does your program actually calculate the centroid coordinates?

Each pixel in the ROI is assigned a "weight" of 1, then
a simple center-of-mass calculation is done:

totalMass = Total(array)
xcm = Total( Total(array, 2) * Indgen(arrayXSize) * scale[0] ) $
/ totalMass
ycm = Total( Total(array, 1) * Indgen(arrayYSize) * scale[1] ) $
/ totalMass
center = [xcm, ycm]

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: ian.j.ashpole on Tue, 04 September 2012 04:35
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: David Fanning on Mon, 03 September 2012 09:26
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: David Fanning on Mon, 03 September 2012 09:24
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: ian.j.ashpole on Mon, 03 September 2012 06:58
		Re: finding the center of gravity of an irregularly shaped roi within a 2d array By: David Fanning on Mon, 03 September 2012 06:42

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