Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!sdd.hp.com!decwrl!adobe!heaven!glenn
From: glenn@heaven.woodside.ca.us (Glenn Reid)
Newsgroups: comp.lang.postscript
Subject: Re: How to super-impose images ?
Message-ID: <219@heaven.woodside.ca.us>
Date: 24 Jul 90 19:49:40 GMT
References: <31377@eerie.acsu.Buffalo.EDU>
Reply-To: glenn@heaven.UUCP (Glenn Reid)
Distribution: usa
Organization: Skyline Press, Woodside CA
Lines: 18

In article <31377@eerie.acsu.Buffalo.EDU> cchang@acsu.buffalo.edu writes:
>But instead of getting the desired result, our second image 
>completely overwrites the first one.  Does anyone know how 
>to do an OR operation on two images ?  

There is no "OR" operation in PostScript, but you can probably get
the result you want by using the "imagemask" operator instead of
the "image" operator.  This operator only writes the bits that
correspond to the mask you specify, which sounds like what you want.
However, it doesn't support gray-scale images, only black and white.
But that doesn't sound like a problem in your case.

/Glenn

-- 
 Glenn Reid				PostScript/NeXT consultant
 glenn@heaven.woodside.ca.us		Independent Software Developer
 ..{adobe,next}!heaven!glenn		415-851-1785