To provide a color image forming apparatus that stably outputs a special color without generating gradation whitening and gradation black crush by density-correcting the prescribed special color in the same control as a single color.
When the special color is set by a user, special color decomposition patch images ms, cs, ys, and ks of magenta, cyan, yellow and black obtained to decompose the special color are added to gradation patterns M, C, Y, K. For instance, two patches m25, m26 whose gradations are near to the special color decomposition patch ms in the gradation pattern M are gradation-modified so as to halve a gradation difference between the special color decomposition patch ms whose gradation is near to the patches m25, m26 and a patch m24, and a gradation difference between the special color decomposition patch ms and a patch m27 respectively. The gradation patterns C, Y, K are also modified. The gradation patterns after modification formed on a recording medium are read with an image reading part to prepare γ tables.
COPYRIGHT: (C)2009,JPO&INPIT
Yu Watanabe
Hiroomi Nakatsuji
Kenji Katsuharaku
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