As mentioned earlier, our goal here is to fit a parametric model that
describes the shape of the dot at each grid location. This is done
independently for each of the CMY channels using the separations
computed as described in Section 4.2.
The actual dot shapes we encountered in scanned prints are rather
varied, and we were unable to obtain good results using a simple
parametric model, such as a disk or a Gaussian. After some experimentation
we chose modeling the dots as radially symmetric, with
the profile consisting of two C
1
connected cubic Hermite splines.
This model is able to approximate the observed dot shapes well using
a total of six degrees of freedom.