Digital Image Watermarking Robustness

A Comparative Study

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Watermarking is the process of inserting predefined patterns into multimedia data in a way that the degradation of quality is minimized and remain at an imperceptible level. Many digital watermarking algorithms have been proposed in special and transform domains. The techniques in the spatial domain still have relatively low-bit capacity and are not resistant enough to lossy image compression and other image processing operations. For instance, a simple noise in the image may eliminate the watermark. On the other hand, frequency domain-based techniques can embed more bits for watermark and are more robust to attack. Some transforms such as Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) are used for watermarking in the frequency domain. In this thesis, we compare the DCT watermarking algorithms and especially the DWT watermarking algorithms based on robustness criteria. In other words, the robustness of different transform watermark algorithms is evaluated by applying different attacks. One main reason to consider the DWT watermarking algorithms is that several multimedia standards such as the JPEG2000 and MPEG-4 are based on the DWT. These new standards brought new requirements such as progressive, low bit rate transmission, and region-of-interest coding.