Game Development Reference
In-Depth Information
Fig. 2.3
RGB additive color model and CMYK subtractive color model.
a
Attribution: “1416 Color
Sensitivity” by OpenStax College—Anatomy and Physiology, Connexions Web site.
http://cnx.org/
content/col11496/1.6/
,
Jun 19, 2013;
b
Attribution: “SubtractiveColor” by Original uploader was
SharkDat en.wikipedia Later version uploaded by Jacobolus, Daciumat en.wikipedia.—Transferred
from en.wikipedia. Licensed under Public domain via Wikimedia Commons
all possible chromaticities at that luminance. Figure
2.4
shows the color gamut of
sRGB, Adobe RGB and CIE xyY color space. CIE xyY color space is a variation of
CIE XYZ color space, where
x
and
y
are the normalized values with three tristimulus
values
X
,
Y
, and
Z
:
X
x
=
(2.1)
X
+
Y
+
Z
Y
y
=
(2.2)
X
+
Y
+
Z
Besides the above RGB and XYZ color spaces, many other color spaces have been
developed for different kinds of applications, e.g., CMYK (cyan, magenta, yellow,
and black), HSV (hue, saturation, and value), HSL (hue, saturation, and lightness),
CIE Lab, YUV, YIQ, and YCbCr, etc. CMYK is usually used in color printing, which
is a subtractive color mixingmodel and describes what kind of inks need to be applied
so the light reflected from the substrate and through the inks produces a given color.
RGB and CMYK are oriented to the hardware devices, while HSV and HSL are
oriented to the users, which is more intuitive for the users to do color adjustment.
CIE Lab is a color-opponent spaces, where L denotes lightness. a and b are the
opponent color. CIE Lab is developed for measuring the perceptually uniform color
difference, which means that a change of the same amount in a color value should
produce a change of about the same visual importance.
In the actual video applications, as the human eyes are sensitive to the lumi-
nance and insensitive to the colors, the YUV color model is usually used instead
of RGB for the bandwidth reduction, where Y is the luma component, and UV
are the chroma component which can be downsampled for data reduction. YUV is
