Patent ID: 8284438

Claim:
An image forming method to perform printing for a plurality of sheets of paper, comprising: receiving print data for printing a printing image and an additional image on each sheet of paper from the plurality of sheets; expressing any one region of the additional image in a first color, the additional image including a predetermined number of regions which are provided at an end part of each sheet of the plurality of sheets of paper and which are continuous in an extending direction of the end part of the sheets; expressing the remaining regions from the predetermined number of regions of the additional image in a second color; and printing the printing image together with the additional image on each sheet of paper such that the one region of the additional image expressed in the first color is shifted sequentially in the extending direction of the end part of the sheets, in an order of the printing of each sheet of paper, wherein the additional image includes a plurality of images; the predetermined number of regions are respectively provided for a plurality of numbers which differ from each other, and the plurality of additional images, which respectively correspond to the plurality of numbers which differ from each other, are printed in the end part of each sheet at positions which differ from each other, and when the printing is performed normally to each sheet of paper and when each sheet of paper is layered on each other in order, a geometric pattern is formed with respect to each region on a side surface of a bundle of printed sheets of paper, each geometric pattern being different from each other.