Adaptive public watermarking of DCT-based compressed images

We propose an adaptive scheme to embed watermark information in DCT blocks of compressed image data. our scheme is designed to avoid artifacts and prevent an increase in the bit rate of the compressed watermarked image. This is essentially done by judicious selection of appropriate blocks for watermark insertion. We also introduce a block-dependent seed generation algorithm to determine the specific coefficients to modify in a particular block. Our proposed technique is simple to implement in software, and hence suitable for real-time software-only insertion of invisible watermarks in JPEG compressed images, and MPEG or MJPEG video streams. We also demonstrate experimentally that our proposed watermarking scheme actually results in bit rate reduction of JPEG compressed images. The proposed technique can also complement existing DCT-based watermarking schemes for copy protection and detection applications.