1. An apparatus for generating image data to produce a print in which characters are hidden, wherein the characters appear when the print is reproduced, the apparatus comprising: a generation unit that generates image data of a size equal to least common multiples from among a size of data representing a bigger dot, a size of data representing a smaller dot, a size of data representing a position of a white region, and a size of data representing boundary between a layout region of the bigger dot and a layout region of the smaller dot, wherein the boundary is a form of the characters; and a creation unit that creates print data for producing the print by repeatedly laying out the generated image data.