The white
paper reflects all visible wavelengths almost evenly; the dyes or pigments deposited
on the paper absorb certain colors, effectively subtracting undesired wavelengths
from the light reflected by the paper. The colors used (subtractive primaries) are the
complements of red, green, and blue: cyan, magenta, and yellow. To make it easier
(and cheaper) to modulate the intensity of light, black is usually also used; since the
color code for black is K, this color system is usually called CMYK (cyan, magenta,
yellow, black).
Color spaces are the mathematical models that allow colors to be represented using a
particular color system. For example, sRGB is a standardized RGB color space
9.2
136 Chapter 9: Color
created in 1995 by HP and Microsoft and endorsed by many companies and organizations
for use on consumer computer electronics such as monitors, digital cameras,
and printers. The W3C has endorsed the sRGB standard for use on the Web. (http://
www.w3.org/Graphics/Color/sRGB is referenced in specifications such as the HTML
4.01 at http://www.w3.org/TR/html4/.)
There are many other ways of describing color in addition to the RGB and CYMK
schemes; the International Commission on Illumination, or Commission Internationale
de l??™Eclairage (CIE), is the international authority on these matters and has defined
several very precise color spaces.
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