Transparent Halftoning

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2 total messages Started by Jerry . Gonzalez Fri, 02 Oct 1992 16:33

#3932

Author: Jerry . Gonzalez
Date: Fri, 02 Oct 1992 16:33

15 lines
930 bytes

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.

Any help would be greatly appreciated!! 

Thanks,

Jerry

Re: Transparent Halftoning

#3954

Author: Peter Davis
Date: Tue, 06 Oct 1992 15:13

26 lines
1580 bytes

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.


                   /
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        /  /  /  /		Peter Davis,	Digital Equipment Corp.
       /  /  /  /				davis@3d.enet.dec.com
      /__/__/__/
     /
  __/

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