A Study on DWT-Based Digital Image Watermarking

基於離散小波轉換的數位影像浮水印之探討

王彥鈞(Yen-Chun Wang)

指導教授 ： 陳朝欽

國立清華大學/電機資訊學院/資訊系統與應用研究所/碩士(2012年)

摘要

在近幾十年間，由於網路技術與應用的發展，數位多媒體快速地成長。為了預防非法使用者未經允許就能輕易地下載與複製數位多媒體資料，近來數位浮水印在版權保護以及所有權認證中的重要性與日俱增。因為其優秀的多重解析度分析以及空間-頻率局部化的能力，離散小波轉換在數位浮水印中被廣泛地運用。因此，本論文的研究目的在於探討數位浮水印與離散小波轉換之間的關係。本論文提出一個浮水印系統，分別將浮水印嵌入在二階與三階小波轉換的中頻係數中，以調查其對於強健性以及透明度的影響。本論文的實驗使用5/3以及9/7小波轉換以檢視本浮水印系統的成效，實驗結果顯示本浮水印系統在經由各種攻擊實驗包含縮放、平滑處理、加入雜訊、中值濾波、JPEG壓縮以及剪裁處理後能滿足強健性以及透明度。總結而言，本論文的實驗結果顯示使用不同型態的小波轉換對本浮水印系統的表現具有顯著的影響，我們希望本論文能夠促使對於數位浮水印與離散小波轉換之間的關係有更清楚地了解。

關鍵字

浮水印 ； 離散小波轉換

並列摘要

During the last few decades, there has been a rapid growth of digital multimedia due to the development of internet technologies and applications. In order to prevent some illegal users who may easily download and copy digital multimedia data without permission, digital watermarking has gathered great importance in the area of copyright protection and owner identification in recent years. Discrete wavelet transform (DWT) has been widely used for digital watermarking due to its excellent multi-resolution analysis and spatial-frequency localization. Thus, the purpose of this thesis attempts to study the relationship between digital watermarking and DWT. This thesis proposes a watermarking scheme that embeds watermarks into the wavelet coefficients of high-low (HL) and low-high (LH) frequency bands of 2-scale and 3-scale wavelet transforms to investigate their effects on robustness and transparency. The experiments of this thesis involves “5/3” and “9/7” wavelet transforms to examine the effects of our watermarking scheme, and the experimental results show that our watermarking scheme satisfies robustness and transparency after a variety of attacks including scaling, smoothing, noise adding, median filtering, JPEG compression, and cropping. In conclusion, the experimental results of this thesis show a distinct effect of using different kinds of wavelet transforms on performance in our watermarking scheme, we are hopeful that this thesis will contribute to a better understanding of the relationship between digital watermarking and DWT.

並列關鍵字

Watermarking ； Discrete Wavelet Transform

參考文獻

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