Prediction-Based Watermarking Schemes for DCT-Based Image Coding
This study presents two predicted-based watermarking schemes, namely Ahead AC-Predicted Watermarking (AAPW) and Post AC-Predicted Watermarking (PAPW), by embedding information into low frequency AC coefficients of Discrete Cosine Transform (DCT). The proposed methods utilize the DC values of the neighboring blocks to predict the AC coefficients of the center block. The low frequency AC coefficients are modified to carry watermark information. The Least Mean Squares (LMS) is employed to yield the intermediate filters for cooperating with the neighboring DC coefficients to predict the original AC coefficients. During the LMS filter training, the training blocks are classified into different categories according to their texture angles and variances. The classified trained filter sets are then used to predict the AC coefficients even more precisely. As documented in the experimental results, the image quality and the embedded capacity of the proposed schemes are superior to former methods in the literature. Moreover, many attacks are addressed to show the robustness of the proposed methods.