Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!ucsd!helios.ee.lbl.gov!surf.ee.lbl.gov!jef
From: jef@surf.ee.lbl.gov (Jef Poskanzer)
Newsgroups: comp.lang.postscript
Subject: Re: How to paint a non-rectangular image?
Message-ID: <4833@helios.ee.lbl.gov>
Date: 10 Feb 90 23:22:24 GMT
References: <1990Feb10.014607.7631@intercon.com>
Sender: usenet@helios.ee.lbl.gov
Reply-To: Jef Poskanzer <jef@well.sf.ca.us>
Organization: Paratheo-Anametamystikhood Of Eris Esoteric, Ada Lovelace Cabal
Lines: 32
X-Local-Date: 10 Feb 90 15:22:24 PST

In the referenced message, amanda@mermaid.intercon.com (Amanda Walker) wrote:
}What I would do is to do two imagemask commands.  The first paints the
}mask bitmap with white, and the second paints the image bitmap in black
}(or whatever).

Hmmmmmm....  This doesn't solve the precise problem I posed, since I
want to paint a grayscale image, but it's very close.  With a little
image hacking using my PBMPLUS toolkit I was able to make this trick
work quite well.  Thanks!

For the benefit of any other PBMPLUS/PostScript hackers out there
(and for my own future reference), here's what I did:

    pgmtopbm face.pgm > face.pbm
    {manually edit face.pbm to remove background, giving clipped.pbm}
    pbmmask clipped.pbm | pnminvert > mask.pbm
    pnmenlarge 5 face.pgm > face5.pgm
    pnmenlarge 5 mask.pbm > mask5.pbm
    ppmarith -mul face5.pgm mask5.pbm | ppmtopgm | pgmtopbm > clipped5.pbm
    pgmtops mask5.pbm > mask5.ps
    pgmtopbm clipped5.pbm > clipped5.ps

Then turn mask5.ps into an imagemask command with invert true and
0 setgray; turn clipped5.ps into an imagemask with invert true and
1 setgray; and adjust the translate and scale commands to shrink
the result back down by a factor of five.
---
Jef

  Jef Poskanzer  jef@well.sf.ca.us  {ucbvax, apple, hplabs}!well!jef
  A witty saying proves nothing, but saying something pointless gets
                          people's attention.