- 學位論文
基於JPEG壓縮下改善透明度及強韌度之離散餘弦轉換浮水印技術
Improving Invisibility and Robustness for DCT-Based Image Watermarking against JPEG Compression
摘要
數位浮水印技術可以用來保護著作人數位著作的財產權。數位浮水印技術可使得數位著作的擁有者在數位著作內容當中嵌入代表擁有者的圖片、標籤或者任何其他數位資訊作為數位簽章。當擁有者的數位著作被盜用時，可從盜用者的手中取出數位簽章以證明所有權，並可以根據著作權法向盜用者申請賠償。 為了提升數位浮水印強韌度，許多相關技術使用離散餘弦轉換將浮水印的資訊加入低頻區，由於低頻區相較於高頻區藏有較多的訊息並可以提供較大的容忍量。這些技術在一般的JPEG壓縮下有著不錯的實驗結果和數據，但是若將JPEG壓縮比往上提高，這些技術下的浮水印將被摧毀。 本論文我們提供了一個創新的離散餘弦轉換的數位圖片浮水印技術，藉由我們提倡的方法可以有效的對抗較高的JPEG壓縮比。我們的技術使用了餘數概念。這項技術也可以保持透明度，維持加過浮水印圖片的視覺質感。
並列摘要
Digital watermarking is the process of embedding information into owner’s contents that is difficult to remove. It can represent in several ways such as an embedded tag, picture, signature or any digital information. Once a digital content has been stolen, owner could use digital watermark to claim the copyright of ownership and apply for compensation according to copyright law. To improve the robustness of digital watermark, most techniques proposed to use discrete cosine transform (DCT) to embed watermark information into the low- frequency part of image since DC components have larger perceptual capacity than AC components. These schemes perform very well under a general JPEG compres- sion. However, when the watermarked images have been compressed with higher compression ratio, the embedded watermark is destroyed. In this thesis, we proposed an innovative DCT-based digital image watermarking scheme that could enhance the robustness under higher JPEG compression with the concept of modulus. We could also preserve the visual quality of watermarked images.