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CMYK
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CMYK

   

CMYK (or sometimes YMCK) is a subtractive color model used in color printing. This color model is based on mixing pigments of the following colors in order to make other colors:

The mixture of ideal CMY colors is subtractive (Cyan, Magenta and Yellow printed together on white result to black). CMYK works through light absorption. The colors that are seen are from the part of light that is not absorbed. In CMYK magenta plus yellow produces red, magenta plus cyan makes blue, cyan plus yellow generates green and the combination of cyan, magenta and yellow form black.

Because the 'black' generated by mixing the subtractive primaries is not as dense as that of a genuine black ink (one that absorbs throughout the visible spectrum), four-color printing uses a fourth, black, ink in addition to the subtractive primaries yellow, magenta and cyan.

Use of four-color printing generates a superior final printed result with greater contrast. However the color a person sees on a computer screen is often slightly different from the color of the same object on a printout since CMYK and the RGB color model used in computer monitors are different. RGB color is made by the emission of light (additive color) whereas CMYK works by the absorption of it (subtractive color).

Table of contents
1 Converting between RGB and CMYK
2 External link

Converting between RGB and CMYK

To convert between RGB and CMYK, we use an intermediate CMY value between them. We have a vector of color values, and we write tCMYK ∈ [0,1]4 is the CMYK quadruple - which means each value of that vector contains values from 0 to 1. Likewise, tCMY ∈ [0,1]3 is the CMY triple, and tRGB ∈ [0, 255]3 is the RGB triple.

Converting CMYK -> RGB

To convert, we first convert CMYK to CMY, then convert the CMY value to RGB

Converting now:

then:
and:

Converting RGB -> CMYK

Converting RGB -> CMY, with the same color vectors as before:
converting to CMY:
and then to CMYK:

where min(x, y, z) is the minimum of those three values.

External link