Graphics - PDF Explained - page 61

• The DeviceGray color space has one additive component, which varies from 0.0
(Black) to 1.0 (White).
• The DeviceRGB color space has three additive components for Red, Green, and
Blue. They each range from 0.0 (e.g., no Red) to 1.0 (e.g., full Red).
• The DeviceCMYK color space has four subtractive components for Cyan, Magenta,
Yellow, and Key (Black). They each range from 0.0 (no pigment) to 1.0 (full pig-
ment).
To change the stroke color space, we use the CS operator. To change the fill color space,
use cs instead. The SC operator (with a number of operands equal to the number of
components in the current color space) can then be used to set the stroke color, or sc
to set the fill color. For example:
/DeviceRGB CS Set stroke color space
0.0 0.5 0.9 SC Set color to RGB (0.0, 0.5, 0.9)

There are shortcut operators for the device color spaces, which set the current stroke
or fill color space and the current stroke or fill color in one operation. These are sum-
marized in Table 5-7 .

Table 5-7. Simple color and color space operators

Operator Operands Function

G 1 Change stroke color space to /DeviceGray and set color

g 1 Change fill color space to /DeviceGray and set color

RG 3 (R, G, B) Change stroke color space to /DeviceRGB and set color

rg 3 (R, G, B) Change fill color space to /DeviceRGB and set color

K 4 (C, M, Y, K) Change stroke color space to /DeviceCMYK and set color

k 4 (C, M, Y, K) Change fill color space to /DeviceCMYK and set color

When a content stream begins, the default color space is /DeviceGray and the default
color value is 0 (fully black), so we can use the g operator straight away:
200 250 100 100 re f
0.25 g
300 250 100 100 re f
0.5 g
400 250 100 100 re f
0.75 g
500 250 100 100 re f
The result is shown in Figure 5-7 .