Method and system for reproducing color images as duotones

Abstract

A full color process image that can be printed with cyan, magenta, yellow, and black inks is produced as a duotone image using only two colors of ink. Color data defining the colors used in the full color image serve as input to a process that maps the colors into a duotone gamut defined by the two colors of ink that will be used to produce the duotone image. A user is able to select 0, 1, or 2 colors of ink for the duotone image, and the software program automatically chooses the remaining ink or inks so as to reproduce the image as accurately as possible; the software also produces the appropriate color separations automatically. In addition, the paper color can be specified by the user or optimally determined by the optimizing process of the software to optimize the duotone image reproducing a full color image that has little white. The paper color provides a free third color. A black separation can also optionally be included when printing the duotone image to expand the range of luminance available. When black ink is used, some amount of black is subtracted from the each color of the original image before the optimization and mapping process is applied, and the black separation is determined to add back the appropriate amount of black when printing the duotone image. The duotone images produced by the method are relatively high-quality, economical alternatives to full-color printing.