[texhax] Transparency or reduced saturation using Graphicx ?

[Pierre MacKay]

Whatever you do is not going to be easy.  What I would do (and I 
recently had to do it with 149 images) is take a screenshot, using 
import if you have it available, convert the image to TIFF, and operate 
on it either with GIMP or with Adobe Streamline, to get the spines of 
all the heavy lines.  With the right Streamline settings you should be 
able to come to a fairly close approximation of the lighter penstrokes 
on the associated image. 

One other approach, which may be precluded because you seem to be 
dealing with a simple Black-White image rather than any level of 
grayscale, would be to convert it to indexed gray-scale (about 15 levels 
should do) in GIMP and then nip away at the outer edges by progressively 
resetting the lighter grays to white.  Then harden up the remaining 
dark-gray to black pixels to simple black. I have found that an 
extremely useful way to fine down slovenly (200DPI) scans of what was 
originally line art, so that the result was an acceptable imitation of a 
1200DPI scan.  But usually you need to start with some reasonable level 
of gray scale, which doesn't seem to be available in your samples.

If only a simple graying out is needed, GIMP layers will do it.  The top 
layer can be set as not fully transparent.

Pierre MacKay