In the exemplary embodiment described above, the image reading apparatus 12, the image processing apparatus 14, the image forming unit 18, the crease forming device 52, and the folding device 54 are integrated, but they may be separate devices that are physically separated from each other. In addition, any two, three, or four of the image reading apparatus 12, the image processing apparatus 14, the image forming unit 18, the crease forming device 52, and the folding device 54 may be integrated to constitute a device. In these cases, the transfer of data between the devices may be performed by electrical connection or by a portable memory such as a USB memory. Further, in these cases, the specified position of the folding line, the amount of deviation of the folding line (including the amount of deviation of the crease or the amount of deviation of the fold), or information based thereon (such as the adjustment value of the device) may be displayed on the display panel or the like.

Further, in the exemplary embodiment described above, the image reading apparatus 12 having the illumination unit 20 in which the amount of light on the second side DirR is smaller than the amount of light on the first side DirL in the sub-scanning direction DM is used, but the image reading apparatus 12 having another illumination unit 20 in which the amount of light on the second side DirR is larger than the amount of light on the first side DirL in the sub-scanning direction DM may be used. The process of specifying a position of the crease using the other illumination unit 20 will be described below with reference to FIGS. 6A, 6B, 7A, 7B, and 8.