[sane-devel] descreen feature request

[QUBE RUBBIK]

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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