[Openicc] Drop size calibration

[Robert Krawitz]

I'm experimenting with another approach to drop size calibration.
This uses the new segmented dither algorithm to print stripes using
different drop sizes.

The exact technique I use is to interleave fixed 10% stripes of a
larger drop size with variable stripes (0-100%) of a smaller drop
size.  I then look for where there's no visible banding; that spot
should indicate where equal amounts of ink are being printed with both
drop sizes.  For example, if there is no banding at 20%, that means
2 small drops are equivalent to 1 large drop.

The only problem I'm having is that this method is yielding very
different results on the RX580 from what I've already tuned, and my
tunings agree with Roy Harrington's.  I've tried with 5% instead of
10%, and get essentially the same results.

Using this method, I've derived ratios of approximately 0.33:0.43:1.00
for the smallest set of drops on the RX580, but the ratios currently
in use are 0.23:0.37:1.00.  For the large drops, I'm getting ratios of
0.17:0.47:1.0 (vs. 0.071:0.30:1.0 that we're currently using).  The
ratio between the small and medium drops in the large set should be
very close to the ratio between the small and large drops in the large
set, but the eyeball approach isn't quite giving that result (it's off
by about 10%).  I'm also seeing slightly different results for cyan
vs. black (by maybe 5%), but that's likely to be within margin of
error for the printer.

Right now I don't know why this is happening, or what it means.  In
any case, this is the testpattern config file that I'm using for this
(you'll need the most recent CVS update for all of this to work
correctly).  Perhaps I'll try these drop sizes and see what happens.

printer "escp2-rx580";
hsize 1.0;
vsize 0.2;
left 0.0;
top 0.0;
mode gray 16;
steps 100;
blackline 0;
parameter "DitherAlgorithm" "Segmented";
parameter "ColorCorrection" "Raw";
parameter "Resolution" "1440x1440ov";
parameter "PrintingMode" "BW";

xpattern 0.5 0.74999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.5 0.74999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.5 0.74999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.5 0.74999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.5 0.74999 1.0;

grid 100;
grid 100;
grid 20;
grid 20;
grid 10;
grid 10;
grid 20;
grid 20;
grid 100;
grid 100;

xpattern 0.55 0.575 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.55 0.575 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.55 0.575 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.55 0.575 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.55 0.575 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.55 0.575 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.55 0.575 1.0;

grid 100;
grid 100;
grid 20;
grid 20;
grid 10;
grid 10;
grid 20;
grid 20;
grid 100;
grid 100;

xpattern 0.3 0.325 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.3 0.325 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.3 0.325 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.3 0.325 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.3 0.325 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.3 0.325 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.3 0.325 1.0;

grid 100;
grid 100;
grid 20;
grid 20;
grid 10;
grid 10;
grid 20;
grid 20;
grid 100;
grid 100;

xpattern 0.25 0.49999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.25 0.49999 1.0;

grid 100;
grid 100;
grid 20;
grid 20;
grid 10;
grid 10;
grid 20;
grid 20;
grid 100;
grid 100;

xpattern 0.25 0.49999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.25 0.49999 1.0;

grid 100;
grid 100;
grid 20;
grid 20;
grid 10;
grid 10;
grid 20;
grid 20;
grid 100;
grid 100;

xpattern 0.75 1 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.75 1 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.75 1 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.75 1 1.0;
xpattern 0.775 0.775 1.0;
xpattern 0.75 1 1.0;

xpattern 0.5 0.74999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.5 0.74999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.5 0.74999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.5 0.74999 1.0;
xpattern 0.525 0.525 1.0;
xpattern 0.5 0.74999 1.0;

xpattern 0.25 0.49999 1.0;
xpattern 0.275 0.275 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.275 0.275 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.275 0.275 1.0;
xpattern 0.25 0.49999 1.0;
xpattern 0.275 0.275 1.0;
xpattern 0.25 0.49999 1.0;

-- 
Robert Krawitz                                     <rlk at alum.mit.edu>

Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail lpf at uunet.uu.net
Project lead for Gutenprint   --    http://gimp-print.sourceforge.net

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