On improving the quality of simple graphics

Abstract

Some colour graphics terminals, such as the Digital Equipment Company (DEC) GIGI terminal, are attractive to use for examining cell layout. But, because of their limited screen memory, such terminals do not define colour on a single-pixel basis. Crossing lines of differing colours lead to annoying colour conflict. Frequently, the result is to display, in the same colour, geometries existing on two or more layers. This results in a confusing picture which most affects students if they have no access to a Design Rule Checking program. The alternative of repeatedly check-plotting leaf-cells leads to a serious bottleneck, when only one hard-copy colour plotter is available, because of the slow plotting speed. The algorithm described herein is simple, reduces the colour conflicts to an acceptable level, and may easily be added to most plotting software.