Digital Watermarking Technique using Discrete Cosine Transform

The proliferation of digitized media due to the rapid growth of networked multimedia systems has created an urgent need for copyright enforcement technologies that can protect copyright ownership of multimedia objects. Digital image watermarking is one such technology that has been developed to protect digital images from illegal manipulations. Different watermarking schemes have been suggested for images. This paper proposes a watermarking algorithm based on image segmentation and discrete cosine transform (DCT). The image is first segmented and then for each segment, the image segment is subdivided into pixels blocks of size 8×8 (64pixels), and zigzag reordered. The DCT of the block is then computed. Then, a pseudorandom sequence of real numbers is embedded in the DCT domain of each image segment. Different experiments are conducted to show the performance of the scheme under different types of attacks. The results show that our proposed watermark scheme is robust to common signal distortions, including geometric manipulations.