Run Length Slice Algorithm for Incremental Lines

Abstract

Lines displayed on devices such as incremental plotters, raster CRT or plasma panel displays, and matrix printers must be approximated by sequences of discrete axial and diagonal unit steps in which successive incremental movements are constrained to the movement pattern of the king piece in a game of chess. Described is a Freeman/Reggiori-like algorithm for generating directly the run lengths of constant direction movement within the step sequence in contrast to generating the sequence in its basic unit step elements. The repetitive loop for generating lengths of alternating runs of solely axial and solely diagonal steps requires only integer addition/subtraction together with a sign test and will be executed at most only half the number of times as the comparable loop used to generate the single unit move sequence one step at a time. The algorithm also can be used to examine repetitive patterns and cycles which occur in rastered lines.