1. An image-processing apparatus which expresses images as bit map data having a latent image area and a background area in order to discourage illegal copying of images, the image-processing apparatus comprising: an image generator which generates a new image by expressing the latent image area with dots of a first dot size and the background area with dots of a second dot size which is different from the first dot size; and an information-attaching unit which receives additional information capable of distinguishing an original image from a copy, wherein the information-attaching unit then attaches the additional information to at least the latent image area of the image generated by the image generator.