Local inking with gray pixels

Abstract

As an electronic pen (16) moves across a display screen (12), a position resolver (14) generates a series of x,y-coordinate positions which are sent to a remote computer system (20) having a relatively high latency or time delay before the positions are processed and intended display information is returned to the memory cells of a memory array (24) which controls the display on the display screen (12). During the time delay, a temporary display of the trajectory is created, preferably in light gray or another distinguishable color. Each x,y-coordinate position is compared (32) with an immediately preceding coordinate position to determine whether the pen has moved. If so, the new coordinate is stored in a memory (36) which stores a preselected number of the most recent coordinate positions and to a toggle circuit (38) which toggles a preselected bit of the display information stored in the corresponding memory cell of the memory array. After a preselected time, determined by clocking the recent coordinate position memory (36), the oldest stored coordinate position is clocked out and display information in the memory cell corresponding to the clocked out coordinate position is retrieved (42) and analyzed (44). If the toggled bit is still in the toggled position, the toggle circuit (38) toggles it back to the initial state. If the preselected bit has been reset by the intended drawing in the interim, it is not altered.