Electronic watermark insertion method, electronic watermark detection method and the rotation angle detection method as well as the digital watermark detection apparatus electronic watermark insertion device, and rotation angle detecting device

摘要

PPROBLEM TO BE SOLVED: To set the range of an angle capable of inserting an electronic watermark to be ≥0 degree and 360 degrees and to set the detection range of the rotation angle of a read image to be ≥0 degree and 360 degrees. PSOLUTION: In the case that up/down decision results of an upper image are "up" and a provisional rotation angle is ≥0 degree and 90 degrees, a final detection rotation angle is equal to the provisional rotation angle. In the case that the up/down decision results of the upper image are "up" and the provisional rotation angle is ≥90 degrees and 180 degrees, the final detection rotation angle is equal to an angle for which 180 degrees are added to the provisional rotation angle. In the case that the up/down decision results of the upper image are "down" and the provisional rotation angle is ≥0 degree and 90 degrees, the final detection rotation angle is equal to an angle for which 180 degrees are added to the provisional rotation angle. In the case that the up/down decision results of the upper image are "down" and the provisional rotation angle is ≥90 degrees and 180 degrees, the final detection rotation angle is equal to the provisional rotation angle. PCOPYRIGHT: (C)2008,JPO&INPIT