Method of producing a color conversion table, image processing apparatus, method of image processing, image forming apparatus and recording media

An image processing apparatus which converts a predetermined bit color image signal to be handled in an image input system for inputting an image to a N bit color image signal, with N as a positive integer, to be handled in an image output system for outputting an image, the apparatus comprising:

• a memory section which stores a N+α bit color output value exceeding a color gamut of the color image signal to be handled in the image output system corresponding to a color input value to be handled in the image input system, the color gamut having gradient values not less than 0 and not more than 2N−1;
• a processing section which reads out the color output value corresponding to the color input value from the memory section, and
• a color converting section which converts the N+α bit color output value to a N bit color image signal to be handled in the image output system.

An image processing method, which is performed by an image processing apparatus for converting a predetermined bit color image signal to be handled in an image input system for inputting an image to a N bit color image signal to be handled in an image output system for outputting an image, N being a positive integer, and the method comprising converting the predetermined bit color image signal to be handled in the image input system to the N bit color image signal to be handled in the image output system based on a N+alpha, bit color output value read out from a color conversion table from which the N+alpha, 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 image input system the color gamut having gradient values not less than 0 and not more than 2N−1.

A computer readable recording medium [having stored thereon] which stores a color conversion table used by an image processing apparatus for converting a predetermined bit color image signal to be handled in an image input system for inputting an image to a N bit color image signal, with N as a positive integer, to be handled in an image output system for outputting an image, the conversion table comprising;

• a N+alpha, bit color output value, with as a positive integer, exceeding a color gamut of a color image signal to be handled in the image output system corresponding to a color input value to be handled in the image input system, the color gamut having gradient values not less than 0 and not more than 2N−1, wherein the N+alpha, bit color output value can be read out of the color conversion table corresponding to the color input value.