[digiKam-users] managing old documents

[Sveinn í Felli]

Salut,

One first thing; improve your original image as much as possible. 
There's far too much difference of light between the upper and lower 
parts of the photo [1], and there's not enough light. Smartphones suffer 
in low lighting conditions. Try to illuminate the manuscript with at 
least two steady light sources, ideally ones where you can control the 
frequency and/or strength. Camera and lights on tripods, please.

You could then experiment with what Gilles suggested, personally I'd 
though start by fiddling with "Levels" either in Digikam or Gimp. Once 
you have a good recipe, you could proceed to batch-processing (but 
according my experience of such old tanned paper, manual tuning will 
always be necessary).

Here are some screenshots:

Levels in Gimp: 
<http://sv1.fellsnet.is/myndvinnsla/dodin/Skj%C3%A1mynd%20fr%C3%A1%202020-05-06%2009-31-52.png>

Levels in Digikam: 
<http://sv1.fellsnet.is/myndvinnsla/dodin/Skj%C3%A1mynd%20fr%C3%A1%202020-05-06%2009-38-27.png>

[1]: 
<http://sv1.fellsnet.is/myndvinnsla/dodin/JEgivUDTH5k_IMG-20200505-144724_v1.jpg>

Just thoughts,
Sveinn í Felli


Þann 6.5.2020 09:17, skrifaði jdd at dodin.org:
> 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