30 January 2003 Character-embedded watermarking algorithm using the fast Hadamard transform for satellite images
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In this paper, a character-embedded watermarking algorithm is proposed for copyright protection of satellite images based on the Fast Hadamard transform (FHT). By using a private-key watermarking scheme, the watermark can be retrieved without using the original image. To increase the invisibility of the watermark, a visual model based on original image characteristics, such as edges and textures are incorporated to determine the watermarking strength factor. This factor determines the strength of watermark bits embedded according to the region complexity of the image. Detailed or coarse areas will be assigned more strength and smooth areas with less strength. Error correction coding is also used to increase the reliability of the information bits. A post-processing technique based on log-polar mapping is incorporated to enhance the robustness against geometric distortion attacks. Experiments showed that the proposed watermarking scheme was able to survive more than 70% of attacks from a common benchmarking tool called Stirmark, and about 90% against Checkmark non-geometric attacks. These attacks were performed on a number of SPOT images of size 512×512×8bit embedded with 32 characters. The proposed FHT algorithm also has the advantage of easy software and hardware implementation as well as speed, comparing to other orthogonal transforms such as Cosine, Fourier and wavelet transform.
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Anthony Tung Shuen Ho, Anthony Tung Shuen Ho, Jun Shen, Jun Shen, Soon Hie Tan, Soon Hie Tan, "Character-embedded watermarking algorithm using the fast Hadamard transform for satellite images", Proc. SPIE 4793, Mathematics of Data/Image Coding, Compression, and Encryption V, with Applications, (30 January 2003); doi: 10.1117/12.451249; https://doi.org/10.1117/12.451249


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