The following is a note from Tom White, a member of the NT print team. He was explaining how the NT halftoning works.
I didn't see the beginning of this thread, so I may not be
addressing the
question, but here I go anyway:
NT has a system level halftoning engine. This engine was
developed originally
for plotters and it only affects bitmaps. Since there are some
cool features
to this halftone engine, it was decided to include the capability
in the
entire print system (namely let the UniDriver and PostScript
drivers have
access).
IN NO WAY IS THIS THE SAME A POSTSCRIPT HALFTONING.
Instead, the PostScript driver is setup by default to use
"Printer
Halftoning". ("Printer Halftoning" lets the
printer decide what line screen
settings to use and just sends down all the data it has). If the
user
chooses, he can turn system halftoning "on" and get
access to bitmap only
halftoning and manual color adjustment. ("System
Halftoning" does the
halftoning for bitmaps on the client, and only sends down the
bits that are
going to print).
It has been near the top of the "to do list" for NT PS
driver, to add PS
halftoning to the driver. In this case, the PS driver would
present to the
user the PS halftone information found in the PPD and allow the
user to
select from those preset line screens and angles, or define their
own. This
would be similar to what you see today in the Win95/Adobe driver
and in many
DTP apps and would apply to ALL the object on a PS page.
This won't be in 4.0, but look for it soon after.
Tom