OSA-UCS Demonstration Applet

This demonstration applet requires Java 1.1 or higher.

The OSA Uniform Color System (OSA-UCS) is specified by both analytical equations and a regular lattice of discrete points achieved by reflective pigments. We can divide the OSA-UCS planes into two distinct sets depending if they are orthogonal to the coordinates or are tilted. The normal vector relative to the screen for viewing the orthogonal planes is (0,0,1); the normal for viewing the tilted planes is (1,1,1). Note that the x and y coordinates are skewed by 45 degrees. The coordinates of the OSA-UCS are L, j, and g.

Only the full-step set is implemented in this applet. The control interface currently implemented is crude and minimal, but is sufficient to navigate the defined planes. Observe that the colors tend towards pastel, as the illuminating light source modeled is the viewing monitor white at full intensity. The OSA-UCS standard was limited by the color gamut achievable by pigments in D6500 Kelvin illumination.

This applet is based on the Macintosh® program I developed during the course of my master's thesis, which is available as a PDF download. The applet requires Java version 1.1+ to run and a minimum of 24-bit color for proper color rendition. The Java source code is available on request. The original development platform was Sun JDK 1.2.2, tested on both Windows 95 and a Linux 2.2 kernel.

The formulae that specify the OSA-UCS L,j,g coordinates can also be found on page 18 of "Color Appearance and Color Difference Specification" by D.H.Brainard.

Copyright © 1989-2000,2012 by Jim W. Lai.