A Novel Semi-Blind Reference Color Image Watermarking using DWT-DCT-SVD
نویسندگان
چکیده
In this paper we propose three robust and semi-blind digital color image watermarking algorithms. These algorithms are based on hybrid transforms using the combination of Discrete Cosine Transform (DCT) and Singular Value Decomposition (SVD), Discrete Wavelet Transform (DWT) and Singular Value Decomposition (SVD), Discrete Wavelet Transform (DWT), Discrete Cosine Transform (DCT) and Singular Value Decomposition (SVD). The original color image is divided to number of blocks. We calculate the spatial frequency of each block. We kept a threshold on this spatial frequency and from this we form a reference image. In the first algorithm we apply DCT on reference image. The singular values of the applied DCT coefficients and singular values of watermark are modified. In the second algorithm we apply DWT on reference image. Then the reference image divided into four sub bands called LL, LH, HL and HH. The singular values of LL band and singular values of watermark are modified. In third algorithm we apply DWT on reference image. Then the reference image divided into four sub bands called LL, LH, HL and HH. We apply DCT on LL band. The singular values of the applied DCT coefficients and singular values of watermark are modified. The performance of the proposed algorithms was evaluated with respect to imperceptibility. The three algorithms
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