Abstract: In this paper we propose a robust digital watermarking system designed to protect image copyrights, based on locating technique. In previous works, most locating watermarking systems were processed in the spatial domain, yet hardly resisted lossy compression; the purpose of this chapter is to propose a new technique to locate a watermark in the frequency domain and then enhance resistance to lossy compression. Expectation value of locating area in the watermarked image remains the property of displacement, although the image incurs attack of lossy compression. In extracting procedures, the system correctly finds a marked area of the watermarked image and then extracts the watermark from the embedded area. What is more, this system can also resist the attacks of shifting and cropping. In general, if the motif of a watermarked image still exists, the system can extract the watermark correctly, even though the image is seriously cropped. On the other hand, if the motif of the image is cropped, the image has no meaning. From experimental results, we find the system resisting simultaneously various attacks and improving the performance as compared with previous works.
Ching-Te Wang , Tung-Shou Chen and Chia-Mei Tu , 2004. Robust Digital Image Watermarking System Based on Locating Technique Against Lossy Compression and Cropping . Asian Journal of Information Technology, 3: 1203-1213.