Re: [Gimp-print-devel] Re: Unprint

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

   Date: Sun, 20 Feb 2000 20:56:36 +0000
   From: Dave Hill <da...@mi...>

   Robert L Krawitz wrote:
   > 
   >    Date: Sat, 19 Feb 2000 19:12:28 +0000
   >    From: Dave Hill <da...@mi...>
   > 
   >    I tried with the output of print-2.0.2 and the CMY part
   >    contains no black at all, but in all the 3.x versions back to
   >    20000131, the CMY part contains black smears or shadows (the
   >    K part is fine).
   > 
   > What do you mean that the CMY stuff contains "black" smears or
   > shadows?  The 3.x code will use some amount of CMY mixture to generate
   > gray, depending upon the black level, but that's by intent.

   Hi Robert.

   I mean that there is unwanted black "bleeding" into areas outside
   the supposed black.

   I will try and make you some small files to show you.

That was a real bug, all right.  Actually, it was two bugs:

1) Under certain circumstances, the amount of CMY (but probably not K)
   could grow without bound.  That was the cause of the blobs.
   Basically, if the density was high enough, the algorithm would go
   unstable.  I've fixed it by capping the amount of CMY that can be
   tossed into the dither pool.  The fix isn't perfect -- edges aren't
   perfectly sharp -- but it's stable now.

2) Certain image types (indexed RGB, in particular) did not do the
   density calculation (rescaling the LUT, basically).

Both of these are fixed and committed, and will be in 3.1.0 (and 3.0.7!)

-- 
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

"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton