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Re: New Image Processing Routines [message #47688 is a reply to message #47677]

Fri, 24 February 2006 08:07

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

J.D. Smith writes:

> 2. The ASINCH scaling, which is linear at the low end, and logarithmic
> at the high end (which is about perfect for showing noise properties and
> high contrast features all at once). Robert Lupton wrote such a beast
> in IDL already:
>
> http://cheops1.uchicago.edu/idlhelp/sdssidl/plotting/tvasinh .html
>
> His website links to a little paper describing the method (which has
> some very nice properties, but occasionally produces strange-looking
> images:
>
> http://www.astro.princeton.edu/~rhl/PrettyPictures/
>
> The trick will be coming up with an easier way to set the 2 parameters
> required that affect the scaling.

Ah, this is like a tuned gamma function! Nice. I get it! It
is helpful to have some pictures to view:

alpha = 0.2 ; 0.0 > alpha < 1.0
nonlinear = 8 ; 1 > nonlinear < inf
data = indgen(256)
Plot, asinh(alpha*nonlinear*image)/nonlinear

Now vary alpha and nonlinear and you will see how to "tune"
the function.

Cheers,

David

P.S. Requires the ASTRO library routine ASINH.
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Re: New Image Processing Routines By: David Fanning on Fri, 24 February 2006 13:08
		Re: New Image Processing Routines By: David Fanning on Fri, 24 February 2006 08:07
		Re: New Image Processing Routines By: David Fanning on Thu, 23 February 2006 21:48
		Re: New Image Processing Routines By: jdsmith on Thu, 23 February 2006 19:37
		Re: New Image Processing Routines By: Paolo Grigis on Mon, 06 March 2006 02:20
		Re: New Image Processing Routines By: George N. White III on Sun, 05 March 2006 11:35
		Re: New Image Processing Routines By: Marshall Perrin on Fri, 21 April 2006 05:02

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