To provide a technique for outputting printing image data to a printing device using a colored ink, and a special glossy ink having special gloss, including a field discrimination part for discriminating whether there is an adjacent field, in which a special glossy field that is expressed using the special glossy ink and a color production field that is expressed using the colored ink are adjacent in the direction of the image plane; a special gloss boundary processor for adjusting the image data so that the ink volume of the special glossy ink affixed to the special glossy field is gradually reduced from the special glossy field towards the color production field in a case where an adjacent field is present; and an output part for outputting the printing image data based on the adjusted image data the printing device.