Talking about the points of color separation process

The color separation process is used to digitally scan an original and divide the original into red, green, and blue components. Prior to the development of digital imaging, the traditional method of color separation was to photograph the image three times, each time filtering different light rays with corresponding color filters. However, after separation, the desired result is three gray images representing the red, green, and blue components of the original: The next step is to convert each color separation. When a red component image is generated, the resulting image represents the component of the image cyan. Similarly, shades of green and blue components are also generated so that magenta and yellow color separations are generated accordingly.

Cyan, magenta, and yellow are subtractive primary colors, because each color represents the two additive primary colors that are subtracted from white light by an additive primary color. Cyan, magenta and yellow are the three main pigments in color reproduction. Combining these three colors in printing allows a reasonable copy of the original, but this is not the case in practice. Due to the limitations of ink pigments, the resulting darker colors are more dirty and smeared. In order to solve this problem, we must also make a black version to improve the color of the dark part and improve the contrast of the image. There are many techniques for making this black version from the original image; these techniques include gray component replacement, background color removal, and background color addition.