In recent years digital watermarking techniques have been proposed to protect the copyright of multimedia data. Many different watermarking schemes have been suggested for images. The goal of this paper is to develop a watermarking algorithm based on discrete cosine transform (DCT) and JPEG models for digital images. A pseudo-random sequence of real numbers is embedded in the DCT domain of the image. After embedding, the watermark is adaptive and depends on the local host image characteristic. This will ensure the watermark invisibility. By exploiting the statical properties of the embedded sequence, the mark can be reliably extracted without resorting to the original uncorrupted image. By this, it will be more robust and more invisible than current methods. The method is tested using different types of attack. The results show that the watermark is resistant to attack by filtering and to added noise.
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