# Color Constancy: Generalized Diagonal Transforms Suffice

#

Finlayson, G.D., Drew, M.S., and Funt, B.V., "Color Constancy:
Generalized Diagonal Transforms Suffice",
JOSA-A(11), No. 11, November 1994, pp. 3011-3019.

## Abstract:

This study's main result is to show that
under the conditions imposed by the Maloney-Wandell color constancy
algorithm, whereby illuminants are three dimensional and reflectances
two dimensional (the 3-2 world), color
constancy can be expressed in terms of a simple independent adjustment
of the sensor responses (in other
words, as a von Kries adaptation type of coefficient rule algorithm) as
long as the sensor space is first transformed
to a new basis. A consequence of this result is that any color
constancy algorithm that makes 3-2
assumptions, such as the Maloney-Wandell subspace algorithm, Forsyth's
MWEXT, and the Funt-Drew lightness
algorithm, must effectively calculate a simple von Kries-type scaling
of sensor responses, i.e., a diagonal
matrix. Our results are strong in the sense that no constraint is
placed on the initial spectral sensitivities of
the sensors. In addition to purely theoretical arguments, we present
results from simulations of von Kriestype
color constancy in which the spectra of real illuminants and
reflectances along with the human-conesensitivity
functions are used. The simulations demonstrate that when the cone
sensor space is transformed
to its new basis in the appropriate manner a diagonal matrix supports
nearly optimal color constancy.

Full text (pdf)

Keywords: color constancy, von Kries, chromatic adaptation, color
balancing

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