reading wiring diagrams

[hnjmkl]

I think the poor graphic definition of very old wiring diagrams is a felt problem, to repair a complex circuit you need to enlarge the sheet, but the definition gets even worse; I ask if there is a software able to remove the shadow on the sides of the graphic signs, alphanumeric characters, in short, make a straight line clean and defined, I tried with gimp but no filter works, I try to post a small portion of a circuit.

[TimFox]

A photo-imaging software package (I use Corel Paintshop) has spatial filters that might help.  Paintshop has "high-pass sharpen" that works on architectural photos to do a similar effect.