Page 21 - DCAP504_Computer Graphics

Computer Graphics

2.1.2 CMYK Color Model
The colors cyan (C), magenta (M), yellow (Y) and black (K) (CMYK) is a subtractive color model, which
is mainly used in color print production. This color model is also called as a complementary RGB
model. In this color model, inks of four colors, cyan (C), magenta (M), yellow (Y) and black (K) are used
for defining colors. Every color has some ink amount, whose measurement is done by using percent
starting from 0 to 100, where a value of 100 signifies the application of inks at full intensity. This CMY
color model describes colors using a subtractive process, which closely matches the working principles
of the printer.
The color space of CMYK color model is called subtractive. The application of inks of cyan, magenta,
yellow, and black color to a surface that is white in color, is done for subtracting some color from that
white surface. This method of subtraction finally leads to the creation of the final color. This model is
generally called as CMY model.
The subtraction of all colors by the CMY combination at full intensity renders black color. Nevertheless,
because of impurities that exist in the available CMY inks, complete and equal intensity is made
impossible, and filtering of some RGB light takes place, which renders a muddy brown color. Thus,
with the addition of the black ink CMY color model takes place.
In the CMY model, first the white color is considered, and the suitable primary components are taken
away, to yield a preferred color.

If we subtract or decrease the red color from white color, the color that remains
consists of green and blue, which is nothing but the cyan color.

If the above example is considered from another perspective, the quantity of cyan, the complementary
color of red, can be used in order to control the amount of red, which is equal to one minus the amount
of cyan color. The following figure 2.3 depicts a co-ordinate system using the three primary
complementary colors which are cyan (C), magenta (M), and yellow (Y).

Figure 2.3: Color Co-ordinate System with CMY Colors

Source: Schaum's outline of theory and problems of computer graphics
In the figure 2.3, the corner of the CMY color cube, that is, at (0, 0, 0) represents white color, whereas the
corner of the cube that is at (1, 1, 1) represents black color. CMY color model is mainly used for the
production of printed materials. This is the reason why CMY color model is an important element in
printing.

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