The color separation process is used to digitally scan the manuscript and divide the manuscript into red, green and blue components. Before the development of digital imaging, the traditional method of color separation was to take photos of the image three times, and filter different light with the corresponding color filter each time. However, after color separation, the desired result is 3 gray images, which represent the red, green, and blue components of the original:
The next step is to convert each color separation film. When generating a negative image with a red component, the generated image represents the cyan component of the image. Similarly, a negative picture of the green component and the blue component is also generated, so that the magenta and yellow color separations can be generated accordingly.
Cyan, magenta, and yellow are subtractive primary colors, because each color represents the two additive primary colors that are left after subtracting one additive primary color from white light. Cyan, magenta and yellow are the three main pigments in color reproduction. When these three colors are combined in printing, the original can be copied reasonably, but this is not the case in actual situations. Due to the limitation of ink pigments, the darker colors produced are dirty and stained. In order to solve this problem, a black plate is also made to improve the color of the dark part and improve the contrast of the image. There are already a variety of techniques to make this black plate from the original image; these techniques include gray component replacement, background color removal and background color increase.
