GRADATION CONVERSION CURVE CORRECTING METHOD AND GRADATION CONVERSION CURVE CORRECTING PROGRAM

摘要

PPROBLEM TO BE SOLVED: To provide a technology for suppressing coloration on black characters by appropriately correcting the portion of black region of a gradation conversion curve for converting an input gradation value of image data to an output gradation value. PSOLUTION: In the correcting method of a gradation conversion curve, an input gradation value-concentration value relationship is derived for each color component based on the concentration value which is acquired by measuring concentration of each concentration patch in a test chart containing a specified gradation change pattern as well as an input gradation value corresponding to the concentration patch. Relating to the input gradation value-concentration value relationship, an adjustment factor is calculated for each color component based on the minimum concentration value of the color component of which the concentration value at the lowest input gradation value becomes minimum, and based on the adjustment factor, a basic correction amount for the output gradation value is calculated (#9). At the same time, by multiplying the basic correction amount with a weight factor represented by a decreasing function which depends on the input gradation value, a correction amount for the output gradation value in the black region of each color component is calculated (#10). PCOPYRIGHT: (C)2008,JPO&INPIT