Author Topic: CLEAN in Visual Image Processing?  (Read 2299 times)

Offline dmcclain

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CLEAN in Visual Image Processing?
« on: 2015 December 09 01:32:48 »
In radio astronomy it is very common to have bizarrely shaped PSF's (called beam patterns), and for several decades they have been using an algorithm called CLEAN to clean up radio survey maps to make them appear as they would had one used a perfect, more desirable, beam pattern.

When I blow up the images I process with PI, I see all the minor aberrations that remain, guiding errors, and so on. I'm wondering if there is a similar technique of subtracting out actual PSF's till the background residual image, much like MRT at large scale sizes, remains, then add back a better looking PSF?

The technique is iterative and only subtracts out some fraction of PSF from the brightest bumps in the image in every iteration. My guess is that this is to avoid overcorrecting.

Offline dmcclain

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Re: CLEAN in Visual Image Processing?
« Reply #1 on: 2016 March 08 10:41:52 »
I found some references to a hybrid sigma-CLEAN and Lucy-Richardson deconvolution applied to wavelet multiresolution decompositions of HST images by Keel at Alabama. Wavelet decomposition is used to separate the spatial frequency domains since Lucy-Richardson has a tendency to amplify high frequency noise while working well on large structure, while the opposite is true for sigma-CLEAN.

The advantage I see for the sigma-CLEAN algorithm is that it can accommodate spatially varying PSF and so help remove aberrations from the edges and corner regions of an image.

http://adsabs.harvard.edu/full/1992ASPC...25..173K

http://adsabs.harvard.edu/full/1991PASP..103..723K

Is anyone working on this kind of algorithm for PI? If not, maybe I'll take a stab.

Offline Carlos Milovic

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Re: CLEAN in Visual Image Processing?
« Reply #2 on: 2016 March 08 11:31:15 »
Seems nice. :)

If you want to work on this, you can count on me for advise/help. I would love to go deeper into this and code something, but I don't have enough time to dedicate to other projects at this moment.
Regards,

Carlos Milovic F.
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PixInsight Project Developer
http://www.pixinsight.com

Offline dmcclain

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Re: CLEAN in Visual Image Processing?
« Reply #3 on: 2016 March 08 11:37:20 »
Thanks for the offer. I can handle the image processing DSP stuff just fine. But I'm a neophyte on the PI framework. So I may ping you on that stuff when I get to that point. For now, I'll model it offline in Lisp.