IMAGE PROCESSING APPARATUS, METHOD, AND MEDIUM STORING PROGRAM THEREOF FOR GENERATING IMAGE DATA HAVING A DOT IMAGE USED TO SUPPRESS INFORMATION LEAKAGE

A region of a latent image and that of a background image in a first dot image are converted into binary data so as to have different binary data, and a region of the latent image in the binary data is converted into dot data by expressing that region as dots. A second dot image is converted into outline data by removing dots of a region corresponding to the region of the latent image to form an outline region. The converted dot data and converted outline data are composited to generate a dot image including the outline data as a latent image and the dot data as a background image.