Re: [Gimp-print-devel] Dithers in 3.1.3

[Robert L K. <rl...@al...>]

   Date: Wed, 26 Apr 2000 21:48:41 +0200
   From: Frank van Maarseveen <F.v...@in...>
   Cc: gim...@li...

   On Tue, Apr 25, 2000 at 07:25:16PM -0400, Robert L Krawitz wrote:
   > I'd like something bigger than that.  23x23 is only 469, and that
   > doesn't give enough resolution to handle very pale tones.  73x73 is
   > smaller than ideal also (5329), but it's in the right ballpark.  The
   > matrices currently in use are 128, 81, and 125.  A matrix of size 121
   > (picked out of thin air) would take about 3 weeks to calculate, then.

   Sorry for this dumb question but: you mean the matrix or any picture
   produced with it?

The matrix itself.  Dithering an image from an existing matrix is very
fast.  The matrix would be statically generated.

   Has it been tried to fill such a matrix with the output of a random
   number generator? There are a lot of pretty good RNGs.

Thomas Tonino explained that -- white noise makes a very poor dither
because of the wide range of frequency components.  Blue noise (noise
with dominant high frequency components) would work well, but it's
harder to generate.  That's where a well-designed matrix comes in --
it contains precomputed "noise".

-- 
Robert Krawitz <rl...@al...>      http://www.tiac.net/users/rlk/

Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail lp...@uu...
Project lead for The Gimp Print --  http://gimp-print.sourceforge.net

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