Article View: comp.lang.postscript
Article #3954Re: Transparent Halftoning
From: Peter Davis
Date: Tue, 06 Oct 1992 15:13
Date: Tue, 06 Oct 1992 15:13
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In article <1992Oct2.163303.15592@ringer.cs.utsa.edu>, gonzo@lonestar.utsa.edu (Jerry . Gonzalez) writes...
>
>I was wondering if there is a way to do transparent
>halftoning? Well, let me explain what I'm doing.
>By using PostScript I've already got an image of a
>brain displayed. Now, what I need to do is overlay
>a grid of boxes (filled with different gray tones)
>over the brain. Is there a way to make this boxes
>somewhat transparent so the brain image can still
>be seen under the boxes? Hope thus made sense.
>
You can achieve this by using the imagemask operator to draw a gray tone
pattern, clipped, if desired, to the shape you want to draw. There's no way
to use the built-in setscreen operator, since this always paints both on and
off pixels, ie, it does NOT do transparency. Using imagemask is effective,
but it will be slow.
/
/
/ / / / Peter Davis, Digital Equipment Corp.
/ / / / davis@3d.enet.dec.com
/__/__/__/
/
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Newsgroups: comp.lang.postscript Path: arc1-ca.pugleaf.net!sparky!uunet!charon.amdahl.com!pacbell.com!ames!decwrl!deccrl!news.crl.dec.com!pa.dec.com!engage.pko.dec.com!dssdev.enet.dec.com!davis From: davis@dssdev.enet.dec.com (Peter Davis) Subject: Re: Transparent Halftoning Message-ID: <1992Oct6.141621.8992@engage.pko.dec.com> Sender: newsdaemon@engage.pko.dec.com (USENET News Daemon) Organization: Digital Equipment Corporation References: <1992Oct2.163303.15592@ringer.cs.utsa.edu> Date: Tue, 6 Oct 1992 15:13:18 GMT Lines: 27