Retinex Image Processing--Publications--SPIE 4388, Orlando, Florida
Conference
The Spatial Aspect of
Color and Scientific Implications of Retinex Image Processing
Daniel J. Jobson and, Zia-ur Rahman, Glenn A. Woodell
Abstract
The history of the spatial aspect of color perception is reviewed in order
to lay a foundation for the discussion of retinex image processing. While
retinex computations were originally conceived as a model for color constancy
in human vision, the impact on local contrast and lightness is even more
pronounced than the compensation for changes in the spectral
distribution of scene illuminants. In the multiscale retinex with
color restoration (MSRCR), the goal of the computation is fidelity to
the direct observation of scenes. The primary visual shortcoming of the
recorded image is that dark zones such as shadow zones are perceived
with much lower contrast and lightness than for the direct viewing of
scenes. Extensive development and testing of the MSRCR led us to form
several hypotheses about imaging which appear to be basic and general in
nature. These are: (1) the linear representation of the image is not
usually a good visual representation, (2) retinex image enhancements
tend to approach a statistical ideal which suggests the existence of a
canonical ``visual image", and (3) the mathematical form of the MSRCR
suggests a deterministic definition of visual information which is the
log of the spectral and spatial context ratios for any given image.
These ideas imply that the imaging process should be thought of, not as
a replication process whose goal is minimal distortion, but rather as a
profound non-linear transformation process whose goal is a statistical
ideal visual representation. These insights suggest new directions for
practical advances in bringing higher levels of visual intelligence to
the world of computing.
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