[Openicc] Drop size calibration

[Graeme Gill]

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

I guess I'm a bit puzzled as to why you need such a calibration.
By definition a larger drop is going to result in higher density
than a smaller drop. So as long as the dither/screen progresses
through the dots in order, the result should be monotonic, even
if it's not very linear. As long as the input precision to
the screen/dither is high enough, and the resulting raw screen
transfer curve is smooth enough, the calibration will linearize the
result. Of course to avoid banding artefacts it is important to
crossover from one dot side to the other (ie. there needs to be
overlap of the different dot sizes), so that the pattern never
"fills up" at intermediate dot sizes.

Graeme Gill.