[sane-devel] descreen feature request

[m. allan noah]

We have had several requests for this over the years. However, most of
us that work on SANE are 'scratching our own itches' by providing the
features we need. This is your itch, so brush off your programming
skills or your wallet, and scratch :)

allan

PS- sending us a link to a patented algorithm is a VERY bad idea. If
we implement it, we can no longer claim ignorance of the patent....

2009/3/8 QUBE RUBBIK <qube001 at hotmail.com>:
> Hello Sane freaks
>
>
> I take the keyboard to suggest some descreen feature within the SANE backend
>
> I know it might be considered as a image post processing feature but is not
> IMHO
>
> The goal of descrening is to remove the ugly halftone patterns that appear
> when you scan a offset printed original (newspapers, magazines)
> This ugly pattern is called "moiré" and is resulting from the scan
> resolution VS dots spacing of the original ratio.
>
> The printed dots are on a grid measured in LPI (line per inch) VS the scan
> resolution DPI, each CMYK color halftone layer is also usally rotated from
> 60 deg from each other to avoid some print patterns on magazines.
>
> you may look at this page for fancy diagrams
> http://www.descreen.net/eng/help/descreen/professional/descreen_manual.htm
>
> considering SANE scanning
>
> Suggestion of any kind of blurring/despeckle image are off topic because
> it's somewhat dumb to scan 300dpi file size and blur it to get 100dpi visual
> sharpness.
>
> I think it has to be embedded within the scan backend because of integration
> in openoffice or mail program doesn't allow to "on the fly" post process the
> image.
>
> At this time it is not possible to get a clean scan in openoffice from a
> magazine, due to the lack of descreening in the backend
>
>
> conclusion :
> descreening allows to get a sharp scan of a dotted print, even in low res,
> it *IS* a scan job
>
> Thank you for reading
>
> food for thoughts:
>
> http://www.freepatentsonline.com/7365882.html
> http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/4566097/4566248/04566304.pdf?arnumber=4566304
> ftp://ftp2.picturel.com/pub/xo/web/halftone/peiHalfTone.pdf
>
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