🚀 go-pugleaf

>Is there an easy way to cause the setgray operator to use a finer screen
>i.e. smaller dots in its shading?  Please mail replies to me.  I will 
>post a summary if there is any demand.

Thanks to SNOW@DRYCAS.CLUB.CC.CMU.EDU (ken) for the following reply:
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The operator that controls the halftone screen is "setscreen"...

	<freq> <angle> <spot-fcn> setscreen

It takes 3 parameters:  frequency (in cells per inch), angle, and
the "spot function" (a procedure defining the order to fill the halftone
cell pixels).  Since you only want to change the frequency, you can
do...

	currentscreen 3 -1 roll pop <newfreq> 3 1 roll setscreen

...which will change only the frequency of the default screen, leaving
the rest the same.

This operator is device-specific; that is, the actual settings that
can be achieved depend on device characteristics (PostScript will try
to get as close as it can to the parameters you request), and different
devices may give different results with the same setscreen call.  It is
particularly sensitve to device resolution.

Also, be aware that as you increase the halftone cell frequency you
decrease its size, so it can represent fewer levels of gray.


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Email: amnonb@taux01.nsc.com
Smail: Amnon Baron Cohen
       National Semiconductor