Patent ID: 7922317

Claim:
An ink jet printing apparatus which performs printing on a printing medium by ejecting from a printing head (1) an ink and (2) a reaction liquid which reacts with the ink, the apparatus comprising: a reaction liquid ejection data generator that, on the basis of ink ejection data for ejecting the ink onto a first side of the printing medium, generates reaction liquid ejection data for ejecting the reaction liquid onto a second side opposite the first side of the printing medium; and a controller for printing by ejecting the ink onto the first side of the printing medium based on the ink ejection data and applying the reaction liquid onto the second side opposite the first side of the printing medium by ejecting the reaction liquid from a printing head based on the reaction liquid ejection data, wherein the reaction liquid ejection data generator inverts the ink ejection data to generate the reaction liquid ejection data for applying the reaction liquid onto a position of the second side which corresponds to a position of the first side on which ink is applied.