1. An image generating method performed by a computer, comprising: determining a code area in which a density of an assembly of linear lines, where midpoints are continued, exceeds a threshold in a midpoint image plotting each midpoint of black dots that are continuously arranged in first image data including a first coded image corresponding to data; acquiring the data corresponding to the first coded image based on the code area; generating, based on the acquired data, a second coded image, wherein a size of a configuration element is an integral multiple of a dot size of the first image data; and generating second image data indicating the generated second coded image.