Fooling with 'tops' and 'imgexp' utilities

[David Hinds]

I'm curious about the parameters for the 'tops' program.  I remember reading
that the default halftone screens on Laserwriters were very nonoptimal; are
there some values that work better with 'tops', or are its defaults as good
as they can be?  Also, I can't seem to get a plain white background with my
printed images.  I used the 'invert' program to flip the screen black to
white, but it comes out as a sparse dot pattern on our laser printer.  So,
I tried using 'imgexp {files} 10 245' to force the very light and very dark
areas to true white and black.  When I look at the images before and after
with 'hist', however, they seem to have exactly the same grey scale ranges!
There are still lots of vertices with grey values in the 251..254 range.
'imgexp' does seem to work if I ask for more extreme range reductions.

 -David Hinds
  dhinds at cb-iris.stanford.edu