Evaluation of Performance of Watermarking Techniques and Development of its Support System

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【○!1】 On the evaluation of performance of watermarking techniques and the improvement of watermarking techniques using the evaluation method : In this research, we aim to establish a tool for evaluating the performance of watermarking methods. We have focused on the quantization-based and correlation-based watermarking methods in the frequency domain, and proposed how to evaluate the performance of these methods. In this evaluation method, we measure the quantity of embedded watermark, the quality of watermarked image, the rate of watermark detection, and the robustness against image processings and attacks. Furthermore, we can know where watermark should be embedded in order for a watermarking method to be robust against image processings and attacks. Using this information, we can improve the robustness of the watermark method.【○!2】 Analysis of watermarking systems using digital signal processing technique and its application to design of robust watermarking systems : In this researc … More h, we have concentrated on the watermarking of still images and deal with the quantization-based and correlation-based watermarking methods. We have first presented a model of the watermark embedding and extracting processes and investigated the robustness of the watermarking system against image processings and attacks. Based on the results, it has been clarified how distortion of the watermark occurs by image processing and the reason why the distortion causes detection errors in the watermark extracting procedure. And then we have discussed the performance of the watermarking systems from the view point of quality of the watermarked image, quantity of the embedded watermark data, and robustness of the watermarking system, and given a method for evaluating their performance. Furthermore we have studied an improvement of the watermark extracting process by designing a deconvolution filter that attempts to undo the effect of watermark distortion. The design has been achieved using the deconvolution technique with adaptive algorithms. Numerical experiments with the DCT-based watermarking system have shown good performance. Less