Optimal Linear RGB-to-XYZ Mapping for Color Display Calibration
Funt, B., Ghaffari, R., and Bastani, B., "Optimal Linear RGB-to-XYZ
Mapping for Color Display Calibration" 12th Color Imaging Conference -
Color Science, Systems & Applications, The SunBurst Resort Scottsdale, AZ,
November 2004
Abstract:
Color display calibration, in part, involves mapping
input RGB values to corresponding output values in a
standardized color space such as CIE XYZ. A linear
model for RGB-to-XYZ mapping is based on a 3-by-3
linear transformation matrix T mapping data from
(linearized) RGB to XYZ. Such a mapping is often
determined by least squares regression on the difference
between predicted and measured XYZ values. However,
since displays are calibrated for viewing by human
observers, it likely would be better to optimize relative to
a perceptually uniform color space. Two new methods
are proposed which optimize the total error relative to
CIELAB or CIEDE2000. The first method uses
weighted least squares with weights based on the rate of
change of CIELAB coordinates as a function of change
in XYZ. The second method uses Nedler-Mead
nonlinear optimization to minimize directly in CIELAB
or CIEDE200. Experiments based on calibrating 2 CRT
monitors, 3 LCD monitors and 2 LCD projectors show
significantly better results than the standard least
squares calibration.
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