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Re: [OM] Descreening a scanned image

Subject: Re: [OM] Descreening a scanned image
From: Moose <olymoose@xxxxxxxxx>
Date: Wed, 26 May 2010 12:07:57 -0700
On 5/24/2010 5:45 AM, Dawid Loubser wrote:
> G'MIC (formerly called GreyCStoration) is amazing at de-screening if you get 
> the parameters right, and if
> you're not afraid of the command-line:
>
> http://gmic.sourceforge.net/gimp.shtml
>
> Have a look at this excellent demonstration:
>
> http://cimg.sourceforge.net/greycstoration/img/res_tunisie.html
>
> I have used it for non-linear image scaling, and image in-painting, it's 
> really very impressive, with a correspondingly unimpressive user interface.
>    

I wasn't about to go through endless iterative command line tries at 
this, I installed GIMP, which is much nicer now than last time I tried 
it, then G'MIC as a GIMP plug-in. G'MIC is indeed a very powerful tool.

For this particular image, I tried GIMP filter Despeckle, another 
plug-in, Descreen and several of the G'MIC filters. Despeckle got rid of 
a lot of the screen, but left an overall, obvious pattern effect. 
Descreen was better, but blotchy/blobby. It looks like it might be good 
on cleaner originals with finer screens.

With the G'MIC filters, I could greatly reduce the screen, while holding 
a lot of apparent detail. As far as I could get it to go, though, I had 
a choice between much reduced, but still obvious screen or no visible 
screen, but a blotchiness. Leaving a bit of screen, applying box blur in 
PS to clear that, I though I had done better than with PS alone.

In the end, though, I ended up with maybe a bit more apparent detail, 
but at the cost of an unattractive blotchiness. I tried using a mask to 
get more detail only in the faces, but finally decided I liked the 
slightly smoother version I did and posted before.

I may try Focus Magic, but not this week. I've got mini workshops to 
finish preparing for a weekend retreat.

Moose

Moose

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