Computational Holographic Image Watermarking Algorithm Based on Discrete Cosine Transform
Zhiyue Liu, Anling Wang, Xiaofeng Zhu, Fuping Liu · 2019
In order to improve the robustness and invisibility of watermark, a grayscale computing holographic image watermarking algorithm based on discrete cosine transform has been proposed. First, the watermark image is calculated to generate a hologram to improve the security of the watermark. The carrier image is divided into 4×4 blocks, and each block is separately subjected to discrete cosine transform, and the low-frequency coefficients of each block are extracted to form a new matrix.Then, the watermark image is subjected to discrete cosine transform, and embed it into the carrier image according to prescript embedding rules, thereby completing the embedding process of the watermark.The extraction process is the inverse of the embedding process. The obtained image is decomposed into 4×4 blocks, and each block is subjected to discrete cosine transform, and extracted according to the inverse law of the embedding.Through test, the experimental results of the method show that the proposed algorithm has strong robustness in image clipping, rotation, translation and Gaussian noise attack. It ensures that the watermark is hidden while resisting a certain degree of attack to meet the needs of copyright identification.