[Openicc] Drop size calibration

[Robert Krawitz]

   Date: Tue, 29 Jan 2008 10:01:29 +0100
   From: Gerhard Fuernkranz <nospam456 at gmx.de>

   Robert Krawitz wrote:

   > I need to find some time to investigate Raph Levien's EvenBetter
   > Screening. I'm not certain, but this may be multi-level as well
   > as well as handling multiple inks.

   Oh, and I was always believing that Gutenprint's "Even Tone" screening
   is already yet another implementation of Raph Levien's algorithm.
   Obviously I was wrong...

No, you're correct -- it's based on his earlier EvenTone algorithm.
The EvenBetter algorithm is an enhancement of EvenTone.

   > The code's a bit convoluted because it's vector-optimized (and
   > because it's Ghostscript-based -- I always find Ghostscript code
   > harder to figure out).

   Raph Levien's original code seems to be pretty easy to use
   (independently of GS). Create the EvenBetter object with
   even_better_new(), then call even_better_line() for each scan line,
   feeding the continuous color data of the scan line into the engine
   and getting the dithered pattern out. But there are a couple of
   parameters too, which can be / need to be tuned.

The code is heavily optimized (even to the point of assuming that the
input is RLL compressed!), and it's a matter of fitting it into the
Gutenprint framework.