隨著通訊網路的快速發展，多媒體的檔案能夠輕鬆地被大眾廣為流傳、散播。由於數位產品相當容易遭到複製，所以未被授權的複製品和電子文件將會是真正的挑戰。為了防止非法剽竊的行為且保障合法認證不被侵犯，數位浮水印技術是相當迫切需要的。
我們提出了一個結合兩個方法的系統，一方面是將二值化後的浮水印影像，利用修改經過量化後的中頻係數來作隱藏，另一方面是使用錯誤更正方法，也就是Reed-Solomon codes，來增加對於非法的攻擊之強韌性。前者的方法具有能夠在經過破壞性的壓縮後仍能倖存的能力，其中的破壞性壓縮如：JPEG或JPEG2000；而後者則能夠抵抗突發性或連續性的雜訊，像是影像處理中的裁切，且還可能對於前面提到的對破壞性壓縮的抵抗力有所助益。實驗的結果證實了我們提出數位浮水印方法的可行性與可靠性。

The rapid growth of communication networks allows the widespread distribution of multimedia data in various ways. Since the digital productions are easy to be duplicated, the discouraging unauthorized clone and the illegal distributing of electronic documents are the issues that have to be resolved. For the purpose of protection against the pirate, digital watermarking techniques are emerged to defend the authentication to be infringed.
In this thesis, we present a combined approach that embeds a binary watermark by selectively modifying the quantized middle-frequency coefficients and use an error control scheme, namely Reed-Solomon codes, to increase the robustness of prevention of illegal attacks. The former is capable of surviving in the lossy compression, such as JPEG or JPEG2000, and the latter owns the ability of resisting burst noise, such as image cropping while increasing the affection of the former.
Experimental results demonstrate that our proposed digital watermarking approach is feasible and effectiveness.

Chapter 1 Introduction4
1.1Motivation4
1.2 Basic watermarking principles5
1.3 System overview7
1.4 Organization of thesis10
Chapter 2 Related Works12
2.1 Related survey of watermark12
2.2 Related survey of error control schemes14
Chapter 3 Proposed Watermarking Algorithm17
3.1 Embedding Method17
3.1.1 Discrete Cosine Transform17
3.1.2 Quantization19
3.1.3 Reed-Solomon Codes21
3.1.4 Shuffling31
3.1.5 Embedding Process31
3.1.6 Inverse DCT34
3.2 Extracting Method35
Chapter 4 Experimental Results36
4.1 Experimental environment40
4.2 Experimental result 142
4.2.1 Image cropping operation42
4.2.2 Image blurring operation44
4.2.3 JPEG47
4.2.4 JPEG 200049
4.3 Experimental result 252
4.3.1 Image cropping operation53
4.3.2 Image blurring operation54
4.3.3 JPEG55
4.3.4 JPEG200057
4.4 Experimental result 359
4.4.1 Image cropping operation60
4.4.2 Image blurring operation61
4.4.3 JPEG62
4.4.4 JPEG200064
Chapter 5 Conclusions and Future works66
5.1 Conclusions66
5.2 Future works67
References68

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