1. An image display medium for displaying an image having a first region including a first composite image, the first composite image comprising: a first display image including at least one of a first halftone dot image and a first line image having a first linearity, the first halftone dot image and the first line image having such densities as are not reproduced by copying; and a first latent image incorporated into the first display image including at least one of a second halftone dot image and a second line image having a second linearity, the second halftone dot image and the second line image having such densities as are not reproduced by copying, wherein the first linearity and the second linearity produce different moiré patterns when the first display image and the first latent image are enlarged by a first common optical system.