SECTION 4.5
243
Color Spaces
The
CS
and
SC
operators select the current stroking color space and current
stroking color separately;
RG
sets them in combination. (The
cs
,
sc
, and
rg
opera-
tors perform the same functions for nonstroking operations.) Setting either cur-
rent color space to
DeviceRGB
initializes the red, green, and blue components of
the corresponding current color to 0.0.
DeviceCMYK Color Space
The
DeviceCMYK
color space allows colors to be specified according to the sub-
tractive
CMYK
(cyan-magenta-yellow-black) model typical of printers and other
paper-based output devices. In theory, each of the three standard
process colorants
used in printing (cyan, magenta, and yellow) absorbs one of the additive primary
colors (red, green, and blue, respectively). Black, a fourth standard process colo-
rant, absorbs all of the additive primaries in equal amounts. The four components
in a
DeviceCMYK
color value represent the concentrations of these process colo-
rants. Each component is specified by a number in the range 0.0 to 1.0, where 0.0
denotes the complete absence of a process colorant (that is, absorbs none of the
corresponding additive primary) and 1.0 denotes maximum concentration (ab-
sorbs as much as possible of the additive primary). Note that the sense of these
numbers is opposite to that of
RGB
color components.
DeviceCMYK
color space and a
specific color within that space for stroking operations.
Example 4.4
/DeviceCMYK CS
cyan magenta yellow black
SC
cyan magenta yellow black
K
% Set DeviceCMYK color space
% Set color
% Set both in one operation
The
CS
and
SC
operators select the current stroking color space and current strok-
ing color separately;
K
sets them in combination. (The
cs
,
sc
, and
k
operators per-
form the same functions for nonstroking operations.) Setting either current color
space to
DeviceCMYK
initializes the cyan, magenta, and yellow components of the
corresponding current color to 0.0 and the black component to 1.0.