IMAGE FORMING DEVICE, IMAGE FORMING METHOD, RECORDING MEDIUM, PROGRAM, AND COMPUTER READABLE RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide an image forming device by which a secret image can be rightly decoded and the decoding work can be easily executed even if it is an inexpensive image forming device with low printing accuracy. SOLUTION: The image forming device forms a plurality of share images from the secret image by using a visual decoding type secret dispersion method. A means for reducing the loss of decoding information executes the following procedures: (1) A plurality of the share images arranged on the basis of the transfer direction of a recording medium are printed on the same face of the recording medium at one time. (2) The shape of the sub-pixel group of the share images is changed on the basis of the transfer direction of the recording medium. (3) An ink amount and an exposure amount is adjusted corresponding to the material of the recording medium. A means for reducing loads of the decoding work executes the following procedures: (4) A part of the share images in a plurality of the share images is printed with a mirror image. (5) The share images, in which a plural sets of the share images are prepared to one secret image, are printed so that each set is always overlapped at different phases. (6) A plurality of the share images are arranged at a position of overlapping on both faces of the recording medium, and the share images on one face are printed with the mirror image. COPYRIGHT: (C)2005,JPO&NCIPI