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From: jef@well.sf.ca.us (Jef Poskanzer)
Newsgroups: comp.sys.mac,comp.sys.mac.hardware,comp.lang.postscript
Subject: Re: AppleScan
Message-ID: <16151@well.sf.ca.us>
Date: 14 Feb 90 01:57:12 GMT
References: <1990Feb13.233627.16665@phri.nyu.edu>
Reply-To: Jef Poskanzer <jef@well.sf.ca.us>
Organization: Paratheo-Anametamystikhood Of Eris Esoteric, Ada Lovelace Cabal
Lines: 21

In the referenced message, roy@alanine.phri.nyu.edu (Roy Smith) wrote:
}	                                   The way AppleScan (and,
}apparantly, most other bitmap manipulation programs) work is to take a
}greyscale image and turn it into a halftone bitmap, then send the halftone
}image to the printer.  Wouldn't it be better to just take the greyscale
}image and send it to the printer and let the PostScript machinery do the
}halftone processing?

Yes.  It's almost always better to use the grayscale scanning option
in AppleScan.  If you're going to send the result to a printer, then
as you point out PostScript can do a better job of halftoning than
AppleScan can.  And even if you want a bitmap for screen display,
any of the freely-available bitmap manipulation programs will also
do a better job of halftoning than AppleScan.  For instance, my
PBMPLUS package does zig-zag Floyd-Steinberg error diffusion that
makes AppleScan's dithering look sick.
---
Jef

  Jef Poskanzer  jef@well.sf.ca.us  {ucbvax, apple, hplabs}!well!jef
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