Multiple Watermarking Based on DCT Coefficients Selection

This paper proposes a multiple watermarking scheme based on Discrete Cosine Transform (DCT) coefficients selection. In the proposed method, the multiple watermarks are embedded into the low and / or middle frequency band in DCT domain of the image blocks. Firstly, the texture complexity is calculated, then based on that, two block selection methods are proposed to select the corresponding adjacent blocks. After that, embedding coefficients and reference coefficients are calculated and the multiple watermarks are embedded by adjusting the difference of projection of embedding coefficients and reference coefficients on the spreading vector. In this way, the embedding efficiency is thus improved. In the experiments, cover images of different texture complexity are used, and various attacks have been simulated for evaluation of the proposed watermarking scheme. Experimental results show that the proposed multiple watermarking scheme can achieve a satisfied performance.