[digiKam-users] managing old documents

[Remco Viëtor]

On mercredi 6 mai 2020 11:30:19 CEST Gilles Caulier wrote:
> Hi,
> 
> With this kind of documents, i use :
> 
> -Restoration to remove artifact and increase sharpness.
> -Sharp again with Refocus or Unsharp Mask
> -Change the Gamma or the Contrast.
> -Reduce colors with White Balance : it's better for text
> -And save in lossless format of course for archiving.
> 
> All can be done in BQM in batch. Just found the right settings, save
> in a workflow and voilà... take a coffee and process your items in
> batch.
> 
> Note: in recent release, i integrated the GMicQt tool as digiKam and
> showfoto plugin. This tool has plenty of advanced and intelligent
> filters (too much in fact). Experiment, test, and report here of
> course.
> 
> https://gmic.eu/
> 
> As French is your first language, take a look here and enjoy :
> 
> https://linuxfr.org/news/g-mic-2-7-0-une-rentree-pleine-de-style-pour-le-tra
> itement-d-images
> 
> GMic is a monster...
> 
> Best regards
> 
> Gilles Caulier
> 
> Le mer. 6 mai 2020 à 11:17, jdd at dodin.org <jdd at dodin.org> a écrit :
> > Hello :-)
> > 
> > What I will ask is not about digikam, but showfoto or may be GIMP.
> > 
> > work in progress:
> > 
> > http://dodin.org/luciendodin/index.php?n=Biographie.LucienDodinPereCahier
> > 
> > (sorry, only in french)
> > 
> > It's a document from 1883 (yes, no error :-) by my gran father.
> > 
> > Given the nature of the document: very fragile old paper, too large for
> > a scanner (I couldn't find an A3 scanner at reasonable price), I use
> > photos. Now from a smartphone moto G4+, very good image wise.
> > 
> > But. I get results like this one:
> > 
> > https://www.cjoint.com/doc/20_05/JEgivUDTH5k_IMG-20200505-144724.jpg
> > 
> > pretty hard to read :-(
> > 
> > On a photo forum, a friend said he could have a pretty good result with
> > an application I don't know "color fx pro", obviously not on Linux :-(,
> > that is already much better than the original (for my purpose: better
> > readability)
> > 
> > https://www.cjoint.com/doc/20_05/JEgiMLo0vzP_Untitled.JPG
> > 
> > the setup is:
> > 
> > https://www.cjoint.com/doc/20_05/JEgiMk8lNnP_Capture-d%E2%80%99e%CC%81cran
> > -2020-05-06-a%CC%80-10.37.48.png
> > 
> > obviously it's a tone control that makes clear tones lighters and medium
> > one (text) darker
> > 
> > is there a way to have a similar (or better result with showfoto?
> > eventually with GIMP (I'm much more familiar with showfoto than from
> > gimp)?
> > 
> > thanks
> > jdd
> > --
> > http://dodin.org
In this particular case, what worked rather well for me was channel mixer to 
grayscale with 100% red, followed by using levels (or curve) to improve 
contrast, and a dose of local contrast.

But as usual, there are several ways to get an improved readability of the 
text.