[PLUG] Postscript/Ghostscript question

[Ben Dugan <bdugan@curdes.com>]

I've been using handwritten postscript to make gray-scale wheels that 
are printed on film.  They work as I'd intended, but now I'd like to do 
the same thing but using halftones to make the 'grays', because this 
will mean I can get them printed on high-contrast films that have some 
properties that are preferable.

From what I can see it shouldn't be hard to get halftones, but what 
I've tried hasn't worked.  I'm pasting in a simple example that doesn't 
work for me, wondering if anybody's got a tip.

I'm sorry if this seems off-topic.  I think I recall some past 
postscript questions, but maybe I'm wrong...

It seems to me this example should show giant (5 per inch) halftone 
cells in, for example, gv.  But instead I see nice smooth grays.

-- example

%!PS-Adobe-3.0

% bwd 2005-01-24
% experiments to get halftones instead of grays

/inch { 72 mul } def

4.0 inch 10.0 inch moveto 1.0 inch 2.0 inch lineto
5.5 inch 1.5 inch lineto closepath

/DeviceGray setcolorspace
5 45 {dup mul exch dup mul add 1 exch sub} setscreen

gsave 0.333 setcolor fill
grestore 0.0 setcolor stroke
4.0 inch 10.0 inch moveto 7.5 inch 3.0 inch lineto
5.5 inch 1.5 inch lineto closepath
gsave 0.667 setcolor fill
grestore 0.0 setcolor stroke

showpage


 %%EOF

-- end of example


Thanks in advance!

Ben


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