混合型數位半色調影像浮水印之研究

在本論文中提出一套結合空間域與頻率域之數位半色調影像浮水印演算法。首先，在數位灰階影像轉換為數位半色調影像的過程中嵌入浮水印，避免直接從空間域上做修改，影響半色調影像品質與視覺效果；為了提高浮水印系統嵌入容量與增加強健性，我們在具有空間域浮水印之半色調影像中，利用小波轉換找出紋理變化大以及灰階值極大與極小之區域，當作頻率域浮水印嵌入之特定區塊。之後利用更改特定區塊之高頻係數值，嵌入頻率域浮水印。本文利用Donut Masks Zernike Moment求得具有混合型浮水印之半色調影像的旋轉角度與縮放倍率之參數，進而抵抗多重攻擊。實驗結果說明本文所提出之數位浮水印系統可抵抗旋轉、縮放、黑色塗鴉、剪裁、胡椒鹽雜訊以及列印與掃瞄攻擊，具有非常好的強健性。

關鍵字

數位半色調影像； Zernike動量；抖陣調色法；二元擬小波轉換

並列摘要

In this thesis, a hybrid watermarking for digital halftone images was proposed. At first, the spatial watermarking was adopted by the ordered dithering technique which uses two dither cells in the digital halftoning. In view of the shortcomings of the spatial watermarking, the spatial watermarked halftone image was divided into sub-images with 8x8 pixels and transformed by binary pseudo-wavelet transform. The frequency watermarking was embedded into the high frequency components of the designated sub-images. Finally, the donut Masks Zernike moment is adopted to detect rotation and scale of the Hybrid watermarked halftone image. Experimental results show that the hybrid watermarked halftone image with high transparency and the is robust to the malicious attacks such as corrupting, cropping, rotating, scaling, salt & pepper noise. The correct decoding rate is close to 0.9 after the attack of print & scan.

並列關鍵字

Halftone Image ； Zernike Moment ； Ordered Dithering ； Binary Pseudo-wavelet Transform

參考文獻

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國際替代計量

混合型數位半色調影像浮水印之研究

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