To perform appropriate dark/light sorting of a specific color while taking account of the quantity of used black ink.

Six color inks of dark cyan, light cyan, dark magenta, light magenta, yellow, and black are used. At a dark/light sorting generation signal generating block 210, a quantity of used ink K1 set for black is multiplied by a first coefficient and added to a quantity of used ink C1 set for cyan thus determining the quantity of dark/light sorting ink C2 for cyan. At a dark/light sorting block 220, temporary quantities C3 and Lc3 of used dark/light ink prepared for cyan are determined based on the quantity of dark/light sorting ink C2 for cyan. At a K component removing block 230, the product of the first coefficient and the quantity of used ink K1 set for black is subtracted preferentially from one of the temporary quantities C3 and Lc3 of used dark cyan and light cyan having a lower lightness.