Color image processing apparatus and color printer system

A color image processing apparatus for generating output gray level values (c4, m4, y4, k4) of four colors including black from input gray level values (c, m, y) of three colors of cyan, magenta and yellow, the color image processing apparatus comprising:

• a first gray level correction unit that makes a gray level correction to the input gray level values (c, m, y);
• a color correction unit that makes a color correction to output values of the first gray level correction unit (c0, m0, y0) to obtain output (c1, m1, y1);
• a minimum value selection unit that selects a minimum value k0 of the output (c1, m1, y1);
• a first calculation unit that calculates a generation amount k3 of black based on the minimum value k0;
• a second calculation unit that calculates an under color removal amount u (k0) which is a value relevant to the minimum value k0;
• a third calculation unit that outputs a correction coefficient value f (k0) which is a value relevant to the minimum value k0;
• a subtraction unit that subtracts the under color removal amount u (k0) from the output (c1, m1, y1) to generate output (c2, m2, y2);
• a multiplication unit that multiplies the output of the subtraction unit (c2, m2, y2) by the correction coefficient value f (k0);
• a significant bit selection unit that selects a significant bit of a multiplication result of the multiplication unit;
• a second gray level correction unit that makes a gray level correction to the generation amount k3 of black and an output of the multiplication unit (c3, m3, y3) to obtain output gray level values (c4, m4, y4, k4);
• and
• a user interface that allows a user to enter density gray level adjustment parameters of cyan, magenta, yellow, and black;
• wherein an input/output relationship of the first gray level correction unit switches in accordance with the gray level adjustment parameters of cyan, magenta, and yellow;
• and
• wherein an input/output relationship of the first calculation unit switches in accordance with the gray level adjustment parameter of black.

A color printer system comprising:

• a computer that creates and edits RGB image data described in three primary colors of red, green and blue;
• an image processing section that processes the RGB image data;
• and
• a record section that records a color image on a record medium based on the data processed by the image processing section,
• wherein the image processing section comprises:
• a minimum value selection unit that selects a minimum value k0 of complement data (c1, m1, y1) of the RGB image data;
• a first calculation unit that calculates a generation amount k3 of black based on the minimum value k0;
• a second calculation unit that calculates an under color removal amount u (k0) which is a value relevant to the minimum value k0;
• a third calculation unit that outputs a correction coefficient value f (k0) which is a value relevant to the minimum value k0;
• a subtraction unit that subtracts the under color removal amount u (k0) from the complement data (c1, m1, y1) to generate output (c2, m2, y2);
• a multiplication unit that multiplies the output of the subtraction unit (c2, m2, y2) by the correction coefficient value f (k0);
• a significant bit selection unit that selects a significant bit of a multiplication result of the multiplication unit;
• and
• a gray level correction unit that makes a gray level correction to the generation amount k3 of black and an output of the multiplication unit (c3, m3, y3) to obtain output gray level values (c4, m4, y4, k4).