Color image processing method and apparatus capable of properly determining black quantity
AssigneeFuji Xerox Co., Ltd.
InventorsShinji Kita, Hitoshi Ogatsu
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Abstract
Three input color separation signals are converted to three color signals on a uniform color space. A black quantity to be used for full-black reproduction is determined as the maximum black quantity of an output black signal. Then, an actual black quantity of the output black signal is determined based on the maximum black quantity and a chroma signal obtained from the uniform color signals. Finally, color quantities of respective output color signals other than the output black signal are determined based on the uniform color signals and the actual black quantity thus determined.
Claims14
A color image processing method for generating from input color separation signals of a first set of three colors representing an input image, output color signals of black and a second set of three colors, the method comprising the steps of:
- converting the input color separation signals of the first set of three colors to uniform color signals of three variables on a uniform color space;
- determining a first black quantity to be used for substantially converting the uniform color signals of three variables to color signals of black and two colors of the first set of three colors, the first black quantity being a maximum black quantity of the output black signal;
- determining a second black quantity based on the first black quantity and a chroma signal obtained from the uniform color signals of three variables, the second black quantity being actually used in the output black signal;
- and
- determining color quantities of the respective output color signals of the second set of three colors based on the uniform color signals of three variables, and the second black quantity.
A color image processing method for generating from input color separation signals of a first set of three colors representing an input image, output color signals of black and a second set of three colors, the method comprising the steps of:
- converting the input color separation signals of the first set of three colors to uniform color signals of three variables on a uniform color space;
- determining a first black quantity to be used for substantially converting the uniform color signals of three variables to color signals of black and two colors of the first set of three colors, the first black quantity being a maximum black quantity of the output black signal;
- determining a second black quantity based on the first black quantity, a chroma signal obtained from the uniform color signals of three variables, and adjustment information including a mode of the input image and a representative color, the second black quantity being actually used in the output black signal;
- and
- determining color quantities of the respective output color signals of the second set of three colors based on the uniform color signals of three variables and the second black quantity.
A color image processing apparatus for generating from input color separation signals of a first set of three colors representing an input image, output color signals of black and a second set of three colors the method comprising:
- means for converting the input color separation signals of the first set of three colors to uniform color signals of three variables on a uniform color space;
- means for determining a first black quantity to be used for substantially converting the uniform color signals of three variables to color signals of black and two colors of the first set of three colors, the first black quantity being a maximum black quantity of the output black signal;
- means for determining a second black quantity based on the first black quantity and a chroma signal obtained from the uniform color signals of three variables, the second black quantity being actually used in the output black signal;
- and
- means for determining color quantities of the respective output color signals of the second set of three colors based on the uniform color signals of three variables and the second black quantity.
A color image processing apparatus for generating from input color separation signals of a first set of three colors representing an input image, output color signals of black and a second set of three colors the apparatus comprising:
- means for converting the input color separation signals of the first set of three colors to uniform color signals of three variables on a uniform color space;
- means for determining a first black quantity to be used for substantially converting the uniform color signals of three variables to color signals of black and two colors of the first set of three colors, the first black quantity being a maximum black quantity of the output black signal;
- means for determining a second black quantity based on the first black quantity, a chroma signal obtained from the uniform color signals of three variable, and adjustment information including a mode of the input image and a representative color, the second black quantity being actually used in the output black signal;
- and
- means for determining color quantities of the respective output color signals of the second set of three colors based on the uniform color signals of three variables and the second black quantity.
Dependencies are inferred from the claim text.