<title>CMYK transformation with black preservation in color management system</title>

Abstract

A color calibration process and system for CMYK printing with black preservation is described in this paper. This approach is used to create a 4-D lookup table (LUT) off time for a closed-loop workflow or a deviceLink ICC profile at real-time by a smart color management module (CMM) for ICC color management workflow. The output K' in the 4-D LUT or the deviceLink profile is decided by the lightness or density mapping between the input K and the output K' and the black usage of the output printer, and K' is proportional to K. The calibration processes are: 1) to convert the input CMYK (e.g. SWOP CMYK) into a device-independent color space (e.g. CIE CAM97s Jab, CIE L*a*b*, or MLab); 2) gamut mapping; and 3) to convert the in-gamut device-independent color into the output CMYK color space. A major difference of this approach over existing methods is that the input K is carried to the second and the third steps to determine the amount of the output K. Therefore the input K information is not lost during the color transformation. This approach can be applied to both closed-loop color architecture and ICC color management.