Re: [Gimp-print-devel] Halftoning algorithms

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

   Date: Mon, 06 Mar 2000 18:43:47 -0800
   From: Raph Levien <ra...@ac...>

   Basically, the way I'd do it (and will do it if I get any bites) is to
   do it the way big prepress color scanners did it in the '70s, which is a
   big bunch of knobs. You have some global controls for dot gain,
   highlight/midtone/shadow +/- for gray balance (so the CMY overprint gets
   calibrated to the same hue as K), then highlight/midtone/shadow +/- for
   each of RYGCBM colors.

That's more or less what's going on with us -- there are a whole bunch
of knobs (at least internal to the dither engine -- none of them are
brought out to the end user, although there is an API).  The
particular controls that are in there are different, but this kind of
"cut & try" seems like the right thing.  There are so many different
kinds of paper, so many different kinds of ink, so many different
cloggednesses of print heads, that trying to get too scientific is
going to be difficult.

   > I did some one to one comparison of the print plugin and
   > the Windows driver on the weekend, and even though the
   > quality of Robert's code is quite good, it's still far
   > from what I can get under Windows. (Can I admit here
   > that I have vmware running just to print stuff?)

   Right. Incidentally, I have been running the stc600 in 1440x720 highest
   quality.

That's what you get from someone who buys a Photo EX from a friend and
then realizes that he has to somehow get it working under Linux, and
then finds some code floating around and h4X0rz away on it :-) :-) :-)
I've never even seen a 600.  However, the EX has a sufficiently
compatible printhead that I can use the 600 driver, and it certainly
does leave something to be desired.  The EX output is, I daresay,
somewhat better.  Big surprise.

   > You hold the patent to the algorighms (at least that's what I
   > understand from reading your page), so you should be free to
   > license the stuff to open source projects free of charge, but
   > still charge for other licensees. As Eric already mentioned,
   > there is no better resumee for you than to put the code out in
   > the open and use a project like Gimp or GhostScript as "bill
   > board" for the algorithm.

   Right. And I plan to release the code under GPL and the patent under a
   license that allows all GPL software to use it freely. The only question
   is the timing. If I can get somebody to fund development as GPL
   software, it will happen quickly. Otherwise, it will happen more slowly.

The flip side is that people like VA and Red Hat want to actually see
something before they're going to fund it.  Feeding code into the Gimp
plugin that's significantly better than anything else out there, and
having it just plug into Ghostscript, and working towards a real free
print system (Ghostscript isn't enough -- it's a decent back end, but
there needs to be a front end and middleware) is something that might
catch people's attention.

   > The weaving code is IMHO not the problem. It is now stable
   > enough to even work on my STC740 :-) So I would not tamper
   > with it. If you can offer something in regards to the
   > error diffusion algorighm, this would help the quality of
   > the plugin more than anything else.

   Right. If it ain't broke, don't fix it :)

Yeah, except when I get some damn fool idea to clean it up and usually
break something in the process. Nobody's complained since my last
round of commits, so it's possible that I got most of the stuff right,
except for the handful of obscure bugs I found and fixed tonight.
Although it's at the point where I'm dead scared to actually touch
anything in the weave calculation per se :-(  There is a unit test for
it, though.

   > I hope we can work something out together. I'm looking
   > forward to hearing some great news from you,

   Me too.

   I'm going to do what I can to get the GPL licensing issue resolved
   quickly. I'm eager to get the cool stuff out there in the field!

I'd definitely like to help you out somehow, as long as the end result
is that we have something we can put in our GPL'ed stuff.

-- 
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