[Desktop_printing] Smooth dithering

Ralph Giles giles at ghostscript.com
Fri Feb 17 11:35:42 PST 2006


On Fri, Feb 17, 2006 at 07:21:06AM -0500, Robert L Krawitz wrote:

> I believe that the latest version of EvenTone dithering that Raph
> Levien has released can do this; I just haven't had time to study the
> code and implement it.  This is very much something I want to do; if
> anyone has the time to volunteer for this it would get it done a lot
> faster.

The output I've seen looks really, really good. But my understanding is 
that careful development of a colourmap for each device (and paper) is 
important not just for accurate colour rendering but for achieving 
smooth and even dither tone.

A version of Raph's work is in the recently released GPL Ghostscript 
8.50 (as well as the AFPL head of course) along with a profile for
the Epson 2200:

  http://svn.ghostscript.com:8080/ghostscript/tags/ghostscript-8.50-gpl/src/gdevrinkj.c
  http://svn.ghostscript.com:8080/ghostscript/tags/ghostscript-8.50-gpl/src/rinkj/
  http://svn.ghostscript.com:8080/ghostscript/tags/ghostscript-8.50-gpl/lib/rinkj-2200-setup

If anyone wants to give it a try. There is a patent warning in the code; 
but the technology may be used royalty free in free software.

Also, IIRC, one really wants SIMD accelleration when driving large 
format (or just fast) printers. The latest (unreleased) version of
the engine contains some; Raph said he'd consider releasing it as well
if there's interest.

 -r



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