INKJET PRINTING WITH INCREASED GAMUT
A method for determining color separation image data for printing for an ink jet printer. Target colors are determined as a function of location in accordance with the image data, and color separation image data is determined specifying amounts of a fluorescent ink and one or more non-fluorescent reflective inks to be combined to form the target colors when printed on an ink receiver. For target colors having a specified hue angle the amount of the fluorescent ink is decreased as a density of the target color increases beyond a threshold density level.
1 . A method for determining color separation image data for printing, comprising
receiving image data for printing;
determining target colors as a function of location in accordance with the image data;
using a processor to determine color separation image data specifying amounts of a fluorescent ink and one or more non-fluorescent reflective inks to be combined to form the target colors when printed on an ink receiver medium; and
storing the determined color separation image data in a processor-accessible memory;
wherein for target colors having a specified hue angle the amount of the fluorescent ink is decreased as a density of the target color increases beyond a threshold density level.
2 . The method of claim 1 wherein one of the non-fluorescent reflective inks is a black ink, and wherein the amount of the black ink is determined after the amount of the fluorescent ink is determined and before the amounts of any other of the reflective inks are determined.
3 . The method of claim 1 wherein one of non-fluorescent reflective inks is a black ink, and wherein the amount of the black ink color is determined such that the combination of the fluorescent ink and black ink provides a printed color with a hue angle of the fluorescent ink with a density that is within a predetermined range of densities.
4 . The method of claim 1 wherein the amount of one of the reflective inks is determined such that the combination of the fluorescent ink and black ink provides a printed color with a density that is within a predetermined range of densities.
5 . The method of claim 1 wherein when the target color for a particular location is in a range of skin tone target colors and the amount of fluorescent ink is determined to, at least in part, absorb invisible wavelengths of light that excite optical brighteners in the ink receiver medium to reduce an extent to which the optical brighteners emit blue light and to emit light of a color that at least in part offsets any blue light emitted by the optical brighteners.
6 . The method of claim 1 wherein a color gamut that can be formed using a combination of the fluorescent ink color and the one or more reflective ink colors is greater than a conventional color gamut that can be formed using a combination of only the one or more reflective inks.
7 . The method of claim 6 wherein the color gamut does not include colors formed using only the fluorescent ink.
8 . The method of claim 1 wherein a hue angle of one of the reflective inks and a hue angle of the fluorescent ink are the same to within 10 degrees, and wherein the determined amounts of the fluorescent ink and the one of the reflective inks combine to provide a specified density at the hue angle of the fluorescent ink, and wherein the fluorescent ink and the one of the reflective inks are further combined with one or more of the other reflective ink colors to form the target color.
9 . The method of claim 1 wherein a hue angle of the fluorescent ink color is greater than 10 degrees different from a hue angle of any of the one or more reflective ink colors and wherein more than one of the reflective ink colors are determined so that the target color is formed when the more than one reflective ink colors and the fluorescent ink color are printed on the ink receiver medium.
10 . The method of claim 1 wherein a visible color spectrum of the fluorescent ink and a visible color spectrum of one of the reflective inks overlap by at least about 25 percent and wherein the amount of the spectrally overlapping reflective ink increases as the amount of fluorescent ink decreases to achieve greater densities.
11 . The method of claim 1 wherein for target colors having the specified hue angle the amount of the fluorescent ink is increased monotonically as a density of the target color increases up to the threshold density level.
12 . The method of claim 1 further including using an inkjet printer to print the amounts of the fluorescent ink and the one or more non-fluorescent reflective inks specified by the color separation image data at corresponding locations on the ink receiver medium.