Flexible image watermarking in JPEG domain

In contrast to many image watermarking schemes, the suggested method is implemented in the JPEG compressed domain with no transcoding or decompression. Therefore, this scheme is highly efficient in real-time applications and suitable for multimedia information, which is rarely available in an uncompressed form. The proposed watermarking scheme is very flexible, and can be tailored to meet the requirements of different real applications. In order to attain a real-time watermarking capability, the proposed system avoids many of the computation steps associated with JPEG compression. Specifically, the forward and inverse DCT do not require to be calculated, nor do any of the computations associated with quantization. Robustness against JPEG compression and additive noise attacks is achieved with the proposed system. A further advantage of the suggested technique is that it allows a watermark to be detected in an image without referencing to the original image, or to any other information used in the watermark embedding process. At the decoder, only entropy decoding is enough to detect watermark and other steps of image decoding are not necessary for detection. The experimental results show how different capacity can be achieved in the range of 1 to 4096 bits for a grayscale 512×512×8 bit image. The watermarking algorithm reduces the quality about 0.65 dB, which is excellent for a watermarking system in compressed domain.