Piecewise linear modulation model of handwriting

Hao Chen, Oscar E. Agazzi, and Ching Y. Suen

A new piecewise linear modulation model of handwriting is proposed in
this paper.  In this model, the velocity of handwriting trajectory is
modeled as the impulse response of a time varying second order system.
For mathematical tractability, the entire trajectory is segmented into
several non-overlapping frames, while the natural frequency and the
damping factor of the system are assumed to vary linearly with time in
each frame and are continuous along the entire trajectory.  In other
words, handwriting is regarded as an oscillation modulated by a
continuous and piecewise linear signal.  The parameters of this model
are estimated by Powell's optimization algorithm which does not
require the computation of the first order derivative.  The number and
lengths of the frames are decided by a modified binary search
algorithm along with the estimation of parameters.  This model has
achieved very high data compression rate as well as accurate
reproduction of real handwriting.