Media storing code detecting program, code detecting method, and image forming apparatus

A medium storing a program to make a computer to function as a code detecting device, the code detecting device comprises a base line specifying section to extract edges from a scan image obtained by a process of scanning a printed matter in which at least a one-dimensional bar code or a two dimensional code are printed, to extract straight lines from the extracted edges, and to specify the longest straight line as a base line among the extracted straight lines; and a code detecting section to perform a pattern matching for the scan image based on the base line and to detect the one-dimensional bar code or the two dimensional code.