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Re: How to add 5% possion noise for a image in IDL [message #83996 is a reply to message #83995]

Fri, 12 April 2013 04:29

wlandsman
Messages: 743
Registered: June 2000

Senior Member

On Friday, April 12, 2013 4:59:10 AM UTC-4, huiqian...@gmail.com wrote:
> Thank you for replying.

If you use poidev, adapted from Numerical Recipes,
(http://idlastro.gsfc.nasa.gov/ftp/pro/math/poidev.pro ) then you can simply write

im = im + 0.05*poidev(im)

The problem with using the POISSON keyword to RANDOMU is that it only accepts a scalar Poisson mean. So one has to iterate over each value in the image, and compute the Poisson random deviate for that value. Here is some quick (not well tested) code to do this:

function addpoisson,im, seed = seed
; return an image with each value replaced by a Poisson deviate
h = histogram(im, min=0, reverse=rr)
newim = im

for i = 0,N_elements(h)-1 do begin
if h[i] NE 0 then begin
sub = rr[rr[i]:rr[i+1]-1] ;Get subscripts
newim[sub] = randomu(seed,poisson=i)
endif
endfor

return, newim
end

--Wayne

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[Message index]

		Re: How to add 5% possion noise for a image in IDL By: dplatten on Fri, 12 April 2013 06:40
		Re: How to add 5% possion noise for a image in IDL By: wlandsman on Fri, 12 April 2013 04:33
		Re: How to add 5% possion noise for a image in IDL By: wlandsman on Fri, 12 April 2013 04:29

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