1. A computer-readable medium which stores a tint block image generation program for generating tint block image data which forms a tint block image including a latent image portion, which is reproduced during copying, and a background portion, of which output density drops during copying, on a print medium, the program causing a computer to execute: a latent image portion generation step of generating data of a plurality of first dots in the latent image portion; and a background portion generation step of generating data of a plurality of second dots having a second screen ruling, and data of a plurality of third dots which are dispersed among the second dots and of which size is smaller than that of the second dots, in the background portion.