Comments by Mads1967 (Top 5 by date)

Thanks for the try, but "pictureBox1_Paint(null,null);" raises an error!

Well, it does. However, it can not be turned off regarding pictureboxes. I believe it's because the pictureboxes does not require skinning, at therefore thought not to need the necessity to be shut off.
The skinning tool just sits on all paint-events, including the pictureboxes (my theory).

Thank you for the links.
I had already found them, but now I did take a closer look especially on that last one.
Actually, when adjusting the contrast it does approximately the same as I found earlier, and thought it was - well - not the right way to do it: The image somehow turns *very* "yellowish" on places where it should be white.
However, when giving the result in Paint.net a second inspection, it looks like they actually make it black and white when contrast is taken close to the limit. This way an eventual yellow shade vanishes into a white.
I'm not an expert into image manipulation, and there is a lot of parameters I don't know, like saturation, hue, etc.
What I need is something that would turn dark grey letters on a light grey surface into something as close to "black letters on a white surface" as possible.
Maybe the solution is somewhere in the CP article about Image-Processing-using-C after all.