Face Detection and Modeling for Recognition - Biometrics Research ...

⎡ ⎤ ⎡
⎤ ⎡ ⎤ ⎡ ⎤
Y
⎣Cb⎦ = 1 65 129.057 25.064 R 16
⎣−37.945 −74.494 112.439 ⎦ ⎣G⎦ + ⎣128⎦(A.1)
256
Cr
112.439 −94.154 −18.285 B 128
⎡ ⎤ ⎡
⎤ ⎡ ⎤
R
⎣G⎦ = 1 298.082 0 408.583 Y
⎣298.082 −100.291 −208.120⎦
⎣Cb⎦
(A.2)
256
B
298.082 516.411 0 Cr
Figures A.1 (a) and (b) illustrate a set of randomly sampled reproducible colors in
the RGB space and its corresponding set in the Y CbCr space.
(a)
Figure A.1.
(b)
Color spaces: (a) RGB; (b) Y CbCr.
A.2 Nonlinear Transformation
In the Y C b C r color space, we can regard the chroma (C b and C r ) as functions of the
luma (Y ): C b (Y ) and C r (Y ). Let the transformed chroma be C b ′(Y ) and C′ r(Y ). The
nonlinear transformation converts the elongated cluster into a cylinder-like shape,
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