Blind Adaptive Shift Length Watermarking For Digital Images

In recent years, as a result of the development of the network and popularization of the multimedia information, watermark technology has been utilized for ensuring the copyright of digital information. This paper proposed a new blind watermarking algorithm for discrete cosine transform (DCT) based digital images. In the proposed method, the differences of DCT coefficients between original and watermarked information were calculated and performed to determine the adjustment of the watermarked DCT coefficients. Simulation results show that the proposed watermark algorithm not only provided similar robustness as previous watermarking investigations but also improved image quality of the watermarked image and the quantity of hiding information. Moreover, the original image is unnecessary for acquiring the watermark information. In the reconstruction procedure, only two bytes side information was required for digital image codec. The file size of watermarked JPEG compressed image approximates one without watermarking.