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Re: New Image Processing Routines [message #47822 is a reply to message #47699]

Mon, 06 March 2006 02:20

Paolo Grigis
Messages: 171
Registered: December 2003

Senior Member

J.D. Smith wrote:
> Looks good, David. If you really want to impress astronomers, you might
> add a few range compression methods:
>
> 1. histogram equalization (done well, is rare).

> 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).

I have used log(x+const) as a scaling for that purpose (where the ratio of
const to the noise level controls how much the noise is emphasized), and was
quite happy about the results for X-ray dynamic spectrograms.

I guess the results are probably quite similar to the asinh scaling, after all
both functions are close to each other. I'll try out the asinh scaling next
time I'll need that kind of rescaling. Thanks for the tip.

Ciao,
Paolo

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.
>
> JD

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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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