[sane-devel] Descreening halftones

[Quentin Bierent]

well , maybe
I thought this would be efficient to handle the picture cleaning very 
close to the scan process (as in usual scan softwares).
On software side at this time no real descreen feature is available in 
GIMP or else, this is the missing link I advocate for.

 >This "commercial", "binary only" Windows junk software pieces
 >also only do blur and re-sharpen and the like.

not that sure, since some of those software ask the LPI 
<http://en.wikipedia.org/wiki/Lines_per_inch> (not to be mismatched with 
DPI!) and the screens angles in order to compute descreening, as seen in 
professional DTP world (binary Mac junk in that case ;-)

 >You can use ImageMagick, ExactImage, Gimp, etc. to perform those
 >tasks.

yep but as a "crap a dirty" bluring or despeckle workaround, as you 
already mentionned

here is some links about haltones and descreening

http://home.att.net/~cthames/DeScreen1.htm
http://en.wikipedia.org/wiki/Halftone
http://www.descreen.net/eng/soft/descreen/descreen.htm


thank you for reading


------------------

On Friday 27 July 2007 09:39:40 Bertrik Sikken wrote:
 > Quentin Bierent wrote:
 > > Hi there
 > >
 > > I've been checking sane from time to time and a key feature is still
 > > missing at this time
 > > every serious scanner user need descreen feature to get clean scan.
 > > Goole shows it's been various requests about this feature (aka 
detramage)
 > >
 > > Every other descreen "workaround methods" are quality degrading (blur,
 > > despeckle etc etc) only a specific and efficient descreen algorythm
 > > (with LPI and screens angles settings) can do a good job for
 > > profesionnal quality.
 > > This is the only way to get a good resolution scan with a low print
 > > quality original (halftone pictures in newspaper can be acquired and
 > > smoothed WITHOUT sacrifying resolution and final quality)
 > >
 > > This feature is available on every serious scanner software (agfa,
 > > binuscan...)
 > >
 > > I will send some examples later.
 > >
 > > I am aware this feature is tricky to implement but  it will for sure
 > > lift SANE  to new heights...
 >
 > What you propose sounds much like an image processing step, while
 > sane is (currently) more about simply getting the data from the
 > scanner.
 > Before adding image processing to sane itself, I think there should at
 > least be some kind of framework where it can fit in cleanly.


-- 
------------------------------------------------------------------------
*ORDICURE SARL*
Tel : 0870785140 - Fax : 0320240535
31, rue de la Fonderie - 59200 Tourcoing - RCS RXTG 443 136 874
http://www.ordicure.com