An image watermarking algorithm with dual purpose
Tian-Yu Ye · Journal of Optoelectronics·laser · 2011
An image watermarking algorithm with dual-purpose is proposed,which can achieve both content authentication and copyright protection.Firstly,the original image was divided into non-overlapping blocks,and each block was conducted with singular value decomposition(SVD).A robust zero-watermarking sequence was produced by judging the numerical relationship between each block′s biggest singular value and the average of biggest singular values from all blocks.Afterwards,the original image was divided into non-overlapping blocks,and each block was transformed with discrete cosine transformation(DCT).Several high frequency coefficients were adjusted to establish linear numerical relationship between two different DCT coefficients from the same block,and the modified image was received after inverse discrete cosine transformation(IDCT).Content authentication was accomplished by judging whether there was a linear numerical relationship between two relevant DCT coefficients from each block of the tampered image based on DCT's reversibility.Copyright was identified by the similarity between the original robust zero-watermarking sequence and the robust zero-watermarking sequence extracted from the attacked image.The experimental results show that the algorithm has good invisibility,and can achieve both content authentication and copyright protection.