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From: vac@cs.cmu.edu (Vincent Cate)
Newsgroups: alt.graphics.pixutils,comp.lang.postscript
Subject: unscaled bitmaps on postscript printers?
Message-ID: <1991Jun28.220628.10895@cs.cmu.edu>
Date: 28 Jun 91 22:06:28 GMT
Sender: netnews@cs.cmu.edu (USENET News Group Software)
Organization: School of Computer Science, Carnegie Mellon
Lines: 30


I want 1 bit on my bitmap to end up as one dot on a 300 DPI
postscript printer, but my printer seems to still mess with
the bits.

I have a pbm file that I am to printing on a 300 DPI printer.
pbmtops defaults to a times 4 scaling (one bit in the pbm file
goes to a 4 by 4 group of dots on the printer), and I want 
1 for 1, so I use "pgmtops -scale 0.25".  This does get my
1800 by 3000 bit pbm file to come out to 6 inches by 10 inches,
like it should.  However, there are all sorts of artifacts
as if the printer had to scale the image.  The printer is a 
DEC lps40.  

What am I doing wrong?  Is there another way to get a bitmap to
a postscript printer?  pgmtopbm -cluster3 seems to make the 
printer happier but it is not as good an algorithm for converting
from grayscale to a bitmap.

The data that I am printing starts out as a 600 by 1200 gif image 
with 6 bits of gray scale.  I have tried things like this:

giftoppm input.gif | ppmtopgm | pgmnorm | pnmenlarge 3 | pgmtopbm |
      pnmcut 0 300 1800 3000 | pgmtops -scale 0.25

If there is a better way to do this please let me know.

Thanks,

  -- Vince