Reduction of dependence of color appearance on light source
AssigneeSeiko Epson Corporation
InventorYuko Yamamoto
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Abstract
A look up table LUT with specific gray reproduction characteristics is used for converting RGB image data to multi-tone data of ink colors. The gray reproduction characteristics of LUT are set such that the color difference ΔE of a gray color area with an arbitrary tone level in the L*a*b* color system is kept at about 4 or less, assuming that the results are observed under two different light sources, such as standard light D50 and standard light A, respectively.
Claims31
A method for printing images on a printing medium with the aid of a printing device capable of using multiple ink types, comprising the steps of:
- (a) preparing a black ink and multiple types of chromatic primary color inks, each of which has a cyan, magenta, or yellow hue;
- and
- (b) reproducing a gray color area having an arbitrary tone level using one or more types of ink selected from the black ink and the multiple types of chromatic primary color inks such that a color difference ΔE of the gray color area in an L*a*b* color system is kept at about 4 or less when the gray color area is observed under two different light sources, respectively.
A method for printing images on a printing medium with the aid of a printing device capable of using an ink set containing a black ink and multiple types of chromatic primary color inks, each of which has a cyan, magenta, or yellow hue, comprising the steps of:
- (a) preparing a color conversion lookup table for converting first color image data expressed by a first color system to second color image data expressed by a second color system for the ink set;
- (b) converting the first color image data to the second color image data using the color conversion lookup table;
- (c) producing print data representing formation of ink dots at each pixel based on the second color image data;
- and
- (d) printing images in accordance with the print data;
- wherein the color conversion lookup table has gray reproduction characteristics that allow a gray color area having an arbitrary tone level to be reproduced using one or more types of ink selected from the black ink and the multiple types of chromatic primary color inks such that a color difference ΔE of the gray color area in the L*a*b* color system is kept at about 4 or less when the gray color area is observed under two different light sources, respectively.
A method of converting first color image data expressed by a first color system to second color image data expressed by a second color system for an ink set composed of a black ink and multiple types of chromatic primary color inks, each having a cyan, magenta, or yellow hue, the method comprising the steps of:
- (a) preparing a color conversion lookup table for converting first color image data expressed by a first color system to second color image data expressed by a second color system for the ink set;
- and
- (b) converting the first color image data to the second color image data using the color conversion lookup table;
- wherein the color conversion lookup table has gray reproduction characteristics that allow a gray color area having an arbitrary tone level to be reproduced using one or more types of ink selected from the black ink and the multiple types of chromatic primary color inks such that a color difference ΔE of the gray color area in the L*a*b* color system is kept at about 4 or less when the gray color area is observed under two different light sources, respectively.
A method of preparing a color conversion lookup table for converting first color image data expressed by a first color system to second color image data expressed by a second color system for an ink set composed of a black ink and multiple types of chromatic primary color inks, each having a cyan, magenta, or yellow hue, the method comprising the steps of:
- (a) preparing a plurality of gray color patches having a plurality of gray tone levels, respectively, the plurality of gray color patches including a first type of gray color patch printed using the multiple types of chromatic primary color inks but not using the black ink, and a second type of gray color patch printed using the black ink and the multiple types of chromatic primary color inks;
- (b) selecting one of the plurality of gray color patches with respect to each gray tone level such that a color difference ΔE in the L*a*b* color system is kept at about 4 or less when the selected gray color patch is observed under two different light sources, respectively;
- and
- (c) defining input and output of the color conversion lookup table to reproduce the gray color patch selected at each gray tone level.
A printing device for printing images on a printing medium, comprising:
- a print head capable of jetting ink drops of a black ink and multiple types of chromatic primary color inks, each of which has a cyan, magenta, or yellow hue;
- a head driver configured to drive the print head to jet ink drops;
- and
- a controller configured to control the head driver to reproduce a gray color area having an arbitrary tone level using one or more types of ink selected from the black ink and the multiple types of chromatic primary color inks such that a color difference ΔE of the gray color area in an L*a*b* color system is kept at about 4 or less when the gray color area is observed under two different light sources, respectively.
A printing device for printing images on a printing medium, comprising:
- a print head capable of jetting ink drops of a black ink and multiple types of chromatic primary color inks, each of which has a cyan, magenta, or yellow hue;
- a color conversion lookup table usable to convert first color image data expressed by a first color system to second color image data expressed by a second color system for the ink set;
- a color converter configured to convert the first color image data to the second color image data using the color conversion lookup table;
- a print data generator configured to produce print data representing formation of ink dots at each pixel based on the second color image data;
- and
- a head driver configured to drive the print head to jet ink drops in accordance with the print data;
- wherein the color conversion lookup table has gray reproduction characteristics that allow a gray color area having an arbitrary tone level to be reproduced using one or more types of ink selected from the black ink and the multiple types of chromatic primary color inks such that a color difference ΔE of the gray color area in the L*a*b* color system is kept at about 4 or less when the gray color area is observed under two different light sources, respectively.
A color converter for converting first color image data expressed by a first color system to second color image data expressed by a second color system for an ink set composed of a black ink and multiple types of chromatic primary color inks, each having a cyan, magenta, or yellow hue, the color converter comprising:
- a color conversion lookup table usable to convert first color image data expressed by a first color system to second color image data expressed by a second color system for the ink set;
- and
- a conversion section configured to convert the first color image data to the second color image data using the color conversion lookup table;
- wherein the color conversion lookup table has gray reproduction characteristics that allow a gray color area having an arbitrary tone level to be reproduced using one or more types of ink selected from the black ink and the multiple types of chromatic primary color inks such that a color difference ΔE of the gray color area in the L*a*b* color system is kept at about 4 or less when the gray color area is observed under two different light sources, respectively.
Dependencies are inferred from the claim text.