Image Processing Reference
In-Depth Information
1
0.9
0.8
B
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
G
1
R
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
Fig. 2.5. The edges of the RGB color space and some important lines with the corresponding
colors. The edges behind the visible faces are marked as
dotted
2.5 RGB: Red, Green, Blue Color Space
There exist other color spaces, each offering a desired convenience in applications
it is intended for, but all relate to CIE-XYZ space. The RGB color space is one
such space that is widely used by millions of devices, including nearly all TV sets,
computer displays, projectors. From experimentally determined
XY Z
values of the
three primaries, the RGB space is obtained via the linear (coordinate) transformation
⎛
⎞
⎛
⎞
⎛
⎞
R
G
B
2
.
36461
−
0
.
89654
−
0
.
46807
X
Y
Z
⎝
⎠
=
⎝
⎠
·
⎝
⎠
−
0
.
51517 1
.
42641
0
.
08876
(2.6)
0
.
00520
−
0
.
01441 1
.
00920
In the additive model, a mixture of colors using positive amounts from the primaries
R,G,B results in a new color. Assuming that the amount mixed from each primary
is in the interval [0
,
1], the resulting color will be represented by a point in a cube,
having the red, green, blue basis as the orthogonal edges of a cube (Fig. 2.5). The
vertices marked as R, G and B define a triangle in the CIE color diagram above. The
triangle represents the gamut of the printer having its primary colors as those marked
with R, G and B. The gray line in one of the main diagonals represents the luminosity
variation available to the RGB space. It consists of colors having equal components
of red, green and blue. Two colors that are complementary have red, green and blue
components that sum to 1
,
1
,
1, respectively.
