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標題: 基於小波轉換之安全性展頻數位浮水印
Wavelet Base Secure Spread Spectrum Image Watermarking
作者: 許孝成
Hsu, Hsiao-Cheng
關鍵字: wavelet transform;小波轉換;digital image watermarking;spread spectrum;PN-Code;數位影像浮水印;展頻;隨機碼
出版社: 電機工程學系
在本篇論文中,小波轉換、展頻PN-Code與多層偵測技術將被運用來完成數位浮水印嵌入程序。首先,原始影像利用小波轉換將影像從空間域轉換到頻域。之後,我們為了保護這嵌入的浮水印,所以我們再利用展頻PN-Code與Modulo-2 運算子來加以保密。在我們的方法上,我們是將浮水印輕微的嵌入到三階小波轉換後的LL3 sub-band。為了有效提升取出浮水印的效能,我們提出一種多層偵測技術的方法。從實驗結果上可以佐證,我們的方法是具有強韌度,不管是嚴重的影像破壞或是大壓縮比的JPEG 與 JPEG 2000的壓縮破壞,浮水印都能存活下來。

The digital watermarks should be hided and invisible by the human visual system. The spread spectrum techniques are used to achieve the goal. The original image is transformed form spatial domain to frequency domain by using discrete wavelet transform (DWT). We insert the spread spectrum PN-code and use modulo-2 operator to secure the watermark. The watermark is embedded into the LL3 sub-band after 3 times DWT. A multilevel detection is proposed to effectively watermark which can increase the retrieval performance. Form the experimental result, the proposed method is robust even under heavy attacks. For example, big compression ratio for JPEG and JPEG 2000, the retrieval watermarks still survive.
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