Hi Graeme,
>Even then how do you completely remove shadows, darkened areas, staples, etc from the magazine or book centre line?
To get an even white background though the scan has some shadows or traces of the text on the backside of the scanned pages, the "curves" function (as I think it's called in software like Photoshop or - free - Gimp) is very useful.
It allows you to assign each source brightness value a target brightness value.
To get rid of the shades, you could for example map all brightness values above 80% to 100% (full brightness).
In a similar way, you could get deep black for the line tracings by assigning all brightness values of 0 to 20% a brightness of 0.
There are no definite values that work for all scans as there is a danger of eliminating light details of the scan by going to 100%, or to "bleed ink" from the black lines by going to 0% of you set the threshold too light. The intermediate brightness values usually occur at the edges of black lines, and if you make them all black, you will get visible pixels and artificially widen the lines.
However, the graphical interface (you can drag points around on a brightness graph, and view the results in a preview) make it easy to find the best combination for each scan by trial and error. Just make sure to check the effect at 100% magnification (or larger) to see the effect on fine detail.
Hope that helps a bit!
Regards,
Henning (HoHun)
Linear Mode
