Data compression for pen stroke input

摘要

A system for compressing pen stroke sequences according to a technique which first outputs an encoding flag indicating a pen touchdown or skipped coordinates, then the absolute values of the first pair of a sequence of horizontal and vertical coordinate pairs, followed by a sequence of nybbles each comprising two bits representing the difference between current and previous horizontal coordinates and two bits representing the difference between current and previous vertical coordinates, an encoding flag being used to terminate each such sequence when either a pen lift off occurs or a delta value exceeds a magnitude of one, the entire sequence being terminated by a further encoding flag. The system allows a high degree of compression to be obtained by storing each difference pair in a single nybble of data, as compared with storing the sequence of absolute coordinates or with known methods storing each difference pair in a single byte, thereby occupying much less memory without losing the ability to reconstruct the original coordinate pair sequence inclusive of any skipped coordinates.