Abstract: A color conversion table for converting M color signals of an input system into N color signals of an output system is disclosed. The color conversion table is prepared by and obtained based on a calculation target point corrected by moving a position of the maximum gradation of each fundamental color of the output system to a position of the maximum gradation of the fundamental color of the input system and on calculation target points corrected for gradations other then the maximum gradation of each fundamental color by moving positions of the gradations of the fundamental color in output system to the positions of the gradations of the fundamental color in the input system.

Abstract: A method for producing a color conversion table by which a color image signal to be handled in an image input system is converted to a N bit color image signal to be handled in an image output system, comprising the step of producing a color conversion table from which a N+? bit color output value, exceeding a color gamut of the color image signal to be handled in the image output system can be read out corresponding to a color input value of the color image signal to be handled in the input system.

Abstract: This invention is directed to an image forming apparatus which forms a color image on the basis of image information and includes an image forming unit which forms a color reference image on an image forming member on the basis of reference image information for color correction, a colorimetric unit which measures the color of the color reference image formed by the image forming unit and outputs color information, an image processing unit which generates a gray level correction table on the basis of the color information output from the colorimetric unit, and a control unit which corrects the image information on the basis of the gray level correction table generated by the image processing unit and controls the image forming unit so as to form a color image on the image forming member on the basis of the corrected image information, and an image forming method using the image forming apparatus.

Abstract: An image processing method for forming a color conversion table to convert plural input colors into output colors, the method including the steps of: extracting color values of plural gray scales wherein in input and output characteristic data, a signal value of one color is variable and signal values of other colors are fixed; creating a model with which difference values between input and output color values are outputted by inputting the extracted color values; and estimating the output color values corresponding to the input color values to create the color conversion table to convert plural input colors into output colors, after shifting the color values by adding or subtracting the difference values which are obtained by inputting the color values into the model with respect to every output color values.

Abstract: A color conversion table for converting M color signals of an input system into N color signals of an output system is disclosed. The color conversion table is prepared by and obtained based on a calculation target point corrected by moving a position of the maximum gradation of each fundamental color of the output system to a position of the maximum gradation of the fundamental color of the input system and on calculation target points corrected for gradations other then the maximum gradation of each fundamental color by moving positions of the gradations of the fundamental color in output system to the positions of the gradations of the fundamental color in the input system.

Abstract: Disclosed is an image reading apparatus, which comprises: (1) an image reading section which scans a calibration sheet for calibration and reads image information thereof; and (2) a correction section which calibrates a brightness tone correction table based on the image information read from the calibration sheet by the image reading section, corrects image information of the calibration sheet using the calibrated brightness tone correction table and calibrates a color correction table based on the corrected image information.

Abstract: A method for producing a color conversion table by which a color image signal to be handled in an image input system is converted to a N bit color image signal to be handled in an image output system, comprising the step of producing a color conversion table from which a N+? bit color output value, exceeding a color gamut of the color image signal to be handled in the image output system can be read out corresponding to a color input value of the color image signal to be handled in the input system.

Abstract: An image processing apparatus for creating a 3D color information conversion table for converting a color image signal of one signal processing system into a color image signal of the other signal processing system, based on color measurement signals obtained by measuring of a reference color original, and image reading signals obtained by reading the reference color originals, the image processing apparatus including: an interpolation processing unit for obtaining output values of the color measurement signals corresponding to RGB input values on four apexes enclosing a RGB input value of a computation target point; and an extrapolation processing unit for obtaining the output values of the color measurement signal corresponding to RGB input values of three apexes enclosing the RGB input value of the computation target point and to a RGB input value of the computation reference point.

Abstract: This invention is directed to an image forming apparatus which forms a color image on the basis of image information and includes an image forming unit which forms a color reference image on an image forming member on the basis of reference image information for color correction, a colorimetric unit which measures the color of the color reference image formed by the image forming unit and outputs color information, an image processing unit which generates a gray level correction table on the basis of the color information output from the colorimetric unit, and a control unit which corrects the image information on the basis of the gray level correction table generated by the image processing unit and controls the image forming unit so as to form a color image on the image forming member on the basis of the corrected image information, and an image forming method using the image forming apparatus.