A robust and blind image watermarking scheme in DCT domain

In this paper, the authors have presented a robust and blind watermarking scheme based on discrete cosine transform (DCT) for protecting the copyright ownership of digital images. Initially, the image is decomposed into non-overlapping blocks and subsequently DCT is employed on each block to embed a binary bit of watermark into each transformed block by modifying some middle significant AC coefficients using repetition code. During the embedding phase of the proposed method, DC and some higher AC coefficients are kept intact after zigzag scanning of each DCT block to ensure the high visual quality of watermarked image. This scheme is suitable to protect the copyright information even in compressed form of the watermarked image since it exploits middle bands of DCT coefficients for embedding the watermark bits. The proposed scheme is also tested to verify the withstand capability against several image processing attacks and satisfactory results are achieved.