Variance-Classified Capacity Watermarking Using Discrete Cosine Transform

This study presents a robust and semi-blind watermarking by embedding information into low frequency AC coefficients of discrete cosine transform (DCT). Since the imperceptibility is the most significant issue in watermarking, the DC value is maintained unchanged. 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, cooperating with the neighboring DC coefficients to precisely predict the original AC coefficients. Two watermarking methods, namely watermark embedding in the predicted AC coefficient (WEPAC) and watermark embedding in the original AC coefficient (WEOAC), are presented in this study. Moreover, many attacks are addressed to show the robustness of the proposed methods.