In this paper, a JPEG domain image watermarking method that utilizes spatial masking is presented. The watermarking algorithm works in the compressed domain, and can be implemented efficiently in real-time (only 50ms is required for a 512x512 24-bit color image on a 700MHz computer). In many applications, particularly those associated with delivering images over the Internet, the ability to watermark images in real-tithe is required. In order to achieve a real-time watermarking capability, the proposed technique avoids many of the computation steps associated with JPEG compression. Specifically, the forward and inverse DCT do not need to be calculated, nor do any of the computations associated with quantization. Robustness to JPEG compression and additive noise attacks is achieved with the proposed system, and the relationship between watermark robustness and watermark position is described. a further advantage of the proposed method is that it allows a watermark to be detected in an image without referencing to the original unwatermarked image, or to any other information used in the watermark embedding process.
