Digital watermark detecting device and method thereof

Abstract

There is provided a digital watermarking detecting device that can accurately detect watermarking information weakened by an attack such as image cut-out, scaling or the like without increasing a calculation amount and a circuit scale. The digital watermarking detecting device includes an extractorfor extracting a signal of a specific frequency component from a watermarking embedded image, first orthogonal transformersA,B for calculating an orthogonally-transformed image of an extraction signal and an orthogonally-transformed image of a watermarking embedded image, amplitude adjustersA,B for adjusting the amplitudes of the two orthogonally-transformed images in accordance with the difference between the amplitude components of the two orthogonally-trans formed images, a compositorfor combining the two amplitude-adjusted orthogonally-transformed images, a second orthogonally-transformerfor subjecting the composite signal to orthogonal transformation to achieve a second orthogonally-transformed signal, and an estimatorfor estimating the watermarking information on the basis of a peak appearing in the second orthogonally-transformed signal.