Roundness in handwriting recognition

In this demo, the relation between roundness and the phase relation between X and Y is shown. The difference between round and sharp handwriting is that in the latter case, wrist and finger movements are more in phase. Round handwriting is characterized by independent wrist and finger movements. In the limiting case, the phase is 90 degrees, yielding circles. To show these effects of differential timing along the two main axes of handwriting, we introduce a global time delay between the X and Y signals (in ms). This is not exactly the same as phase shifting, but has a similar effect on the handwriting shape. Within limits, a given handwritten word can be twisted from round, counter-clockwise looping, via normal, to sharp and clockwise bending. Depending on the letters involved, the trace will become illegible at different delays for different words. Since roundness is a parameter which can be varied by the writer at will, it should be normalized in an automatic recognizer of handwriting (in the ideal case).

How it is done:

     x'(k) = f(x, k + delay)
     y'(k) = f(y, k) 

     where f() is a linear interpolation function applied on the 
     discrete samples, and delay is bounded [-30ms, +30ms].

     Three-point boxcar smoothing is applied to the raw tablet data.

     The trace is truncated where k+delay would refer to a non-existing sample.

Please refer to our Publications when using anything from the shown material.


An interactive demo of controlling roundness in handwriting.

Source code



Up to NICI's Java-based Handwriting Demos page


Other interesting material:

o Handwriting Recognition and Document Analysis Conferences

o Pen & Mobile Computing

o NICI Handwriting Recognition Group home page

o UNIPEN tools


Copyright Lambert Schomaker (April 1, 1996)

since 1/Mar/1996