Patent ID: 8045221

Claim:
An image-processing device comprising: an input unit that inputs image data in which a color of each pixel is expressed by a combination of light's three primary colors, red, green and blue; a color conversion unit that converts the input image data into intermediate image data in which a color of each pixel is expressed by a combination of basic printing colors, cyan, magenta, yellow, and black; a density correction unit that corrects the intermediate image data so that density of each target pixel of the intermediate image data corresponds to density of a pixel of the input image data corresponding to the target pixel; an identifying unit that identifies an area in which density is close to a prescribed value by analyzing the intermediate image data, density of which has been corrected by the density correction unit; and an output unit that corrects a density distribution in a pixel of the intermediate image data contained in the area identified by the identifying unit in accordance with a prescribed distribution function thereby reducing tone jumps, and outputs the result, wherein the identifying unit identifies an area in which density deviation from a reproduction initiation point, which is defined as a minimum density for which a color is reproduced by a combination of the basic printing colors, is equal to or less than a prescribed threshold value; wherein the identifying unit (a) compares, for each pixel of the intermediate image data, density of which has been corrected by the density correction unit, density of a color of the basis printing colors, which is expressed by the pixel, and a reproduction initiation point, which is defined as a minimum density for which the color is reproduced, and (b) identifies an area of pixels in which a difference between the density of the color and the reproduction initiation point is equal to or less than the prescribed threshold value; and wherein the output unit (a) identifies a pixel having a maximum density of the color from among pixels of the intermediate image data contained in the area identified by the identifying unit, (b) adjusts parameters of the prescribed distribution function so that a peak value of the prescribed distribution function conforms to the density of the identified pixel, (c) calculates, for a pixel adjacent to the identified pixel, a value of the prescribed distribution function on the basis of a distance between the adjacent pixel and the identified pixel, (d) compares the calculated value of the prescribed distribution function and density of the color, which is expressed by the adjacent pixel, and (e) if the value of the prescribed distribution function exceeds the density of the color, which is expressed by the adjacent pixel, replaces the density of the color, which is expressed by the adjacent pixel, with the value of the prescribed distribution function.