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Proceedings Paper

The opposite of green is purple?
Author(s): Nathan Moroney
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Paper Abstract

The conventional understanding of opponent colors has red and green as one axis and yellow and blue on a second axis. This perceptual opponency is a result of the trichromatic nature of human color vision in combination with subsequent processing in the visual system. This red-green and yellow-blue opponency is fundamental to many different color spaces. CIELAB, CIELUV, CIECAM02, IPT, YCC and more all incorporate this concept of chromatic opponency. In most cases the yellow and blue opponent axes are reasonable. However for the red-green axis it is more like a purplegreen axis due to a consistent, significant bending of the red-green axis. Is dark purple the opposite of green? This paper summarizes the result of analyzing a wide range of color spaces based on their actual opponency. The consistent limitation of a shared matrix formulation for opponency is discussed and finally a simple, invertible color space is considered. The angular differences between quadrants and computed antonyms is shown to be significantly more consistent using this hypothetical alternative color space.

Paper Details

Date Published: 19 January 2009
PDF: 7 pages
Proc. SPIE 7241, Color Imaging XIV: Displaying, Processing, Hardcopy, and Applications, 72410N (19 January 2009); doi: 10.1117/12.817013
Show Author Affiliations
Nathan Moroney, Hewlett-Packard Labs. (United States)

Published in SPIE Proceedings Vol. 7241:
Color Imaging XIV: Displaying, Processing, Hardcopy, and Applications
Reiner Eschbach; Gabriel G. Marcu; Shoji Tominaga; Alessandro Rizzi, Editor(s)

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