Calculating cyan-magenta-yellow-black (CMYK) printer gray component data based on polynomial modeling

As gray color data is very important for printing quality, a method based on polynomial modeling is proposed to calculate the gray color data of different lightness. Firstly, the IT8.7/3 color target which defines input cyan-magenta-yellow-black (CMYK) signals is printed, and the corresponding CIELAB (Commission Internationale de l'Eclairage L*, a* and b*) values are obtained by a spectrophotometer with color sensors. Secondly, the polynomial regression method is used to determine the relationship between these two color spaces, in which the given CIELAB color’s CMY value is calculated. At last, as the obtained cyan-magenta-yellow (CMY) gray color may contain Chroma information due to the computational error, a new color target is developed to find the real gray colors based on the relationship above, and the final relationship between CIE-L* and CMY are obtained. In the experiment, the average color error is 2.65ΔE, which is below the printing error threshold, hence the proposed algorithm for calculating gray color data can be used in printing process.   Key words: Gray balance, polynomial modeling, CIELAB (Commission Internationale de l'Eclairage L*, a* and b*) color, color sensors.