The method of generating an image in the form of a disc portion on a display, the disc portion comprising a center and a maximum radius defining a limit of the image generated, the disc portion comprising a plurality of angular sectors, each angular sector comprising a plurality of disjoint areas, each disjoint area of an angular sector being delimited by two circular arcs defined between two radii, and each disjoint area being called a “ring”, is characterized in that it comprises: a first step of selecting a ring, a second step of comparing the area of the ring with at least one predefined value, dubbed the grain, a third step of generating the image of the ring as a function of the result of the comparison, a fourth step of incrementing the next ring to be selected.