Image forming apparatus, position detection method, and computer-readable medium

A position detection method comprising:

• printing a plurality of marks on a recording medium with a printing device;
• reading the recording medium on which the marks are printed by the printing device with a scanner;
• first detecting, from image data read by the scanner, positions of outer edges being edges closer to ends of the image data and positions of inner edges being inside edges not closer to the ends of the image data in both of a first direction and a second direction different from the first direction;
• identifying, with respect to a target mark for which a reference position is to be detected and two marks adjacent to the target mark, first line segments connecting the positions of the inner edges and second line segments connecting the positions of the outer edges;
• and
• second detecting, as the reference position of the target mark, a midpoint of a line segment connecting an intersection of the two first line segments connecting the positions of the inner edges and an intersection of the two second line segments connecting the positions of the outer edges.

A non-transitory computer-readable medium including programmed instructions that cause a computer to execute:

• printing a plurality of marks on a recording medium with a printing device;
• reading the recording medium on which the marks are printed by the printing device with a scanner;
• first detecting, from image data read by the scanner, positions of outer edges being edges closer to ends of the image data and positions of inner edges being inside edges not closer to the ends of the image data in both of a first direction and a second direction different from the first direction;
• identifying, with respect to a target mark for which a reference position is to be detected and two marks adjacent to the target mark, first line segments connecting the positions of the inner edges and second line segments connecting the positions of the outer edges;
• and
• second detecting, as the reference position of the target mark, a midpoint of a line segment connecting an intersection of the two first line segments connecting the positions of the inner edges and an intersection of the two second line segments connecting the positions of the outer edges.