1. xvYCC Implementation in the
RGB color space
Shereef Shehata
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2. Why use xvYCC? Better Gamut coverage
sRGB
xvYCC
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3. What is the color gamut
The gamut of any RGB system is mostly visualized by a triangle in xyY. For different luminances
Y=const (or CIECAM02 J = const), we get the intersection of a vertical plane and the RGB cube. The intersection
delivers a polygon. These polygons are projected onto the xy-plane.
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4. xvYCC space for 8-bit representation
• 0<Y_xvYCC_8 < 255
• 0<Cb_xvYCC_8 < 255
• 0<Cr_xvYCC_8 < 255
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5. xvYCC space for 8-bit representation
• 0<Y_xvYCC_8 < 255
• 0<Cb_xvYCC_8 < 255
• 0<Cr_xvYCC_8 < 255
Original space in
blue(RGB in [0,1])
Expanded space in
yellow
A plane describing
R = 1.0
A plane describing
R = 0.
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6. xvYCC space for 8-bit representation
• 0<Y_xvYCC_8 < 255
• 0<Cb_xvYCC_8 < 255
• 0<Cr_xvYCC_8 < 255
Original space in
blue(RGB in [0,1])
Expanded space in
yellow
A Plane
Describing
B = 1.0
A plane
Describing
B = 0.
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7. Extended YCC space: normalized 0:1
representation (gamma corrected)
• -0.068< Y’ < 1.086758
• -0.566964< Cb’ < 0.562500
• -0.566964< Cr’ < 0.562500
• Y’Cb’Cr’ are gamma corrected
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8. xvYCC RGB space: normalized 0:1 representation
(gamma corrected, REC.709)
• -0.9614< R_gamma < 1.9726
• -0.4213< G_gamma < 1.4583
• -1.1206< B_gamma < 2.1306
• Nonlinear gamma exist
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08556.11
4681.01873.01
5748.101
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Cr
Cb
Y
gammaB
gammaG
gammaR
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9. Gamma corrected RGB space: Original vs. xvYCC
• Original RGB space 0<R_gamma, G_gamma, B_gamma < 1: in blue
• Nonlinear gamma exist
Expanded RGB space: in yellow
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10. Linear RGB space: Original vs. xvYCC
• Original Linear RGB space 0<R_lin, G_lin, B_lin < 1: shown in blue
• After de-gamma is performed
Expanded linear
RGB space:
Shown in yellow
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11. Rec.709: Original Gamma function
• The gamma definition as of Rec.709
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12. Gamma function for xvYCC
• The same gamma definition as Rec.709
• Due to the extended range: requires more dynamic range
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13. Gamma Mapping for xvYCC
•The values around Zero expanded & larger
values are compressed (when gamma is
applied)
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14. De-Gamma Mapping for xvYCC
•The values around Zero are compressed &
larger values are expanded (when degamma
is applied)
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15. xvYCC space: Effect on the Red (with gamma)
component
• R_gamma >1 is shown in blue
• R_gamma < 0 is shown in yellow
• 0<R_gamma<1 is shown in red
• R_gamma is gamma corrected Red
Specular Red >1 Negative
Red
Original Red Range
Original space
Shown in black
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16. xvYCC space: Effect on the Red (with gamma)
component
• R_gamma >1 is shown in blue
• R_gamma < 0 is shown in yellow
• 0<R_gamma<1 is shown in red
Specular Red>1
(blue)
Negative
Red (yellow)
Original Red Range
(shown in red, 0<R<1)
Original space, RGB
[0,1] (black)
G<0 and B<0
0<R<1.0 (cyan)
G>1 and B>1
0<R<1 (magenta)
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17. xvYCC space: Effect on the Red (with gamma)
component
• R_gamma >1 is shown in blue
• R_gamma < 0 is shown in yellow
• 0<R_gamma<1 is shown in red
Specular Red>1
(blue)
Negative
Red (yellow)Original space, RGB
[0,1] (black)
G<0 or B<0 and
0<R<1.0 (cyan)
G>1 or B>1 and
0<R<1 (magenta)
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18. 18
TI Proprietary- Strictly
xvYCC space: Effect on the Blue (with gamma)
component
• B_gamma >1 is shown in blue
• B_gamma < 0 is shown in yellow
• 0<B_gamma<1 is shown in red
• B_gamma is gamma corrected B
Negative
Blue
Original Blue Range
Specular Blue>1
Original space
Shown in black

19. xvYCC space: Effect on the Blue (with gamma)
component
Negative Blue (yellow)
Original Blue Range
[0,1] (red)
Specular Blue
>1
R,G,B
in [0,1]
Shown in
(Black)
R?,G? and 0<B<1
R?,G? and 0<B<1
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20. xvYCC space: Effect on the Blue (with gamma)
component
Negative Blue (shown
in yellow)
Original Blue Range
[0,1] shown in (red)
Specular Blue>1
(blue)
R,G,B
in [0,1]
Shown in
Black
R>1,G>1 and 0<B<1
(magenta)
0<B<1,
R<0,G<0
(cyan)
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21. xvYCC space: Effect on the Blue (with gamma)
component
Negative Blue
(shown in yellow)
Specular Blue>1
(blue)
R,G,B in [0,1]
(Black)
0<B<1 and Either R>1 or G>1
(magenta)
0<B<1 and
Either
R<0 or G<0
(cyan)
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22. xvYCC space: Effect on the Green (with gamma)
component
• G_gamma >1 is shown in blue
• G_gamma < 0 is shown in yellow
• 0<G_gamma<1 is shown in red
• G_gamma is gamma corrected G
Negative
Green
Original Green Range
Specular Green >1
Original space
Shown in black
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23. xvYCC space: Effect on the Green (with gamma)
component
• G_gamma >1 is shown in blue
• G_gamma < 0 is shown in yellow
• 0<G_gamma<1 is shown in red
• G_gamma is gamma corrected G
Negative
Green
Original Green Range
Specular Green >1
Original space
Shown in black
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24. xvYCC space: Effect on the Green (linear)
component
• G_lin >1 is shown in blue
• G_lin < 0 is shown in yellow
• 0<G_lin<1 is shown in red
• G_lin is gamma corrected G
Negative
Green
Original Green Range
Specular Green>1
Original space
Shown in black
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25. xvYCC space: Effect on the Green (gamma)
component
Negative
Green
Original Green Range
0<G<1
Specular Green>1
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26. xvYCC space: Effect on the Green (gamma)
component
Negative Green
(yellow)
Original RGB Range
(black)
Specular Green>1
(blue)
0<G<1, Both R<0 and
B <0 (cyan)
0<G<1, Both
R>1 and B>1
(magenta)
Original Green Range
0<G<1 (red)
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27. xvYCC space: Effect on the Green (gamma)
component
Negative Green
(yellow)
Original RGB Range
(black)
Specular Green>1
(blue)
0<G<1, Either
R<0 or B <0
(cyan)
0<G<1, Either
R>1 or B>1
(magenta)
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