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Reducing Staircasing by Using Grey Scale

IP.com Disclosure Number: IPCOM000063681D
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18

Publishing Venue

IBM

Related People

Authors:
Murphy, AS [+details]

Abstract

On a matrix or raster display device which allows the picture elements (pels) to have different brightnesses it is possible to use the variation in brightness to reduce the visual effects of staircasing. The algorithm described below is intended for use in a system where two bits are used to define one out of four brightnesses for each pel. The following illustrates the staircase effect caused by the need to quantize each point on the line to a fixed rectangular array of pels: . . . . X X X X X X X X . . . . The following shows how the same line can be represented when three brightness levels (1, 2 and 3) and black are available: . . 1 1 2 2 3 3 3 3 2 2 1 1 . . The four grey levels are obtained by coding two bits (A-bits and B- bits) for each pel such that the A-bit has the most significant effect on brightness.