Associated information adding apparatus and method, and associated information detecting apparatus and method

Abstract

The present invention relates to an information adding apparatus and method for adding information as a watermark to an image. Particularly, the invention is characterized in that a unit watermark pattern having a size corresponding to a small region made of vertical×horizontal=M×N (M and N are respectively a positive integer) pixels of a part of an image is generated, a repetitive watermark in which the unit watermark pattern from a unit watermark pattern generator is repeated vertically and horizontally is generated, checking is performed against the repetitive watermark, a watermark is added to the image, and in the unit watermark pattern generator, the size of the unit watermark pattern is determined such that at all resolutions expected that resolution conversion for the image is performed, each of the vertical and horizontal sizes of the unit watermark is integer times as large as a size of an encoded block at image encoding. By this, the size of the unit watermark pattern is integer times as large as the size of the encoded block at the image encoding at all resolutions expected that the resolution conversion is performed. Thus, at the time of detection of the associated information, if the resolution of image information is known, it is possible to know, at the resolution, what times as large as the encoded block the unit watermark is, and folding accumulation becomes possible in a unit of the unit watermark of an integer number of encoded blocks