Digital watermark detecting device and method thereof

A digital watermarking detecting device, which detects from a watermarking-embedded image watermarking information that is electrically embedded therein and used in converting a specific frequency component signal extracted from an embedding target image, comprising:

• an extracting processor configured to extract an extraction signal of the specific frequency component from the watermarking-embedded image by an extraction method same with that of a digital watermarking embedding device;
• a first orthogonal transforming processor configured to calculate a primary orthogonally-transformed image by orthogonal transformation of the extraction signal and a secondary orthogonally-transformed image by orthogonal transformation of the watermarking-embedded image;
• an amplitude adjusting processor configured to adjust amplitude of each or either of the primary and secondary orthogonally-transformed images in accordance with a difference between amplitude components of the primary and secondary orthogonally-transformed images;
• a composition processor configured to combine the primary and secondary orthogonally-transformed images thus adjusted in amplitude to provide a composite signal;
• a second orthogonal transforming processor configured to subject the composite signal to orthogonal transformation or inverse orthogonal transformation to provide a second orthogonally-transformed signal;
• and
• a watermarking information estimating processor configured to estimate the watermarking information on the basis of a peak appearing in the second orthogonally-transformed signal.