Patent ID: 7387261

Claim:
An image forming apparatus for forming a code pattern image, the code pattern image having a plurality of code pattern image units, each code pattern image unit including a first region having position-dependent information therein and a second region having position-independent information therein, the position-dependent information being different for each code pattern image unit, the position-independent information being in common for each code pattern image unit, the image forming apparatus comprising: a position-dependent code storage section that stores position-dependent code images, each position-dependent code image corresponding to a distinct position of a code pattern image unit within a code pattern image; a code pattern image generator that generates a code pattern image including a plurality of code pattern image units, each code pattern image unit corresponding to a distinct position in the code pattern image, each code pattern image unit being generated by combining a position-dependent code image stored in the position-dependent code storage section that corresponds to a position of the code pattern image unit within the code pattern image being generated and a position-independent code image representing position-independent information; and an image forming section that forms, onto a surface of a medium, the pattern code image that is generated by the code pattern image generator; said position-dependent code storage section storing, in correlation with each pair of coordinates (x,y) for the respective code pattern image units within the code pattern image, a position-dependent code image corresponding to the pair of coordinates (x,y); said code pattern image generator including, a reader to read out from said position-dependent code storage section, for each pair of coordinates (x,y) of each code pattern image unit, a position-dependent code image corresponding to the coordinates (x,y), and a code pattern image unit generator to generate the code pattern image units by combining, for each pair of coordinates (x,y) of each code pattern image unit, the position-dependent code image corresponding to the coordinates (x,y) read out by said reader and the position-independent code image.