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The Opposite of Green is Purple?

Moroney, Nathan
HP Laboratories


Keyword(s): opponent colors, after images, color spaces, chromatic axes

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 purple-green 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.

7 Pages

Additional Publication Information: To be presented at the Human Vision and Electronic Imaging XIV Conference, San Jose, CA and to be published in SPIE Proceedings Volume 7241.

External Posting Date: March 21, 2009 [Fulltext]. Approved for External Publication
Internal Posting Date: March 21, 2009 [Fulltext]

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