印刷影像於多重色版加密之浮水印技術

Multi-channel Watermarking Technique of Printed Images

本研究針對印刷影像的特性，提出一個新的數位浮水印加密技術，簡稱為多重色版浮水印技術(Multi-channel Watermarking Technique, MCWT)。MCWT可以將圖樣或文字隱藏在印刷影像的多重色版中，並且實際輸出到紙張上。解密時只需使用設計過的光柵透鏡便可直接觀察到所隱藏的資訊，不用經過複雜的計算。實驗結果顯示在青色及洋紅色版中15至30百分比網點面積為最佳的加密條件，同時依相對應的網屏角度來調整網點位置可以獲得較良好的解密效果。

In this paper, we proposed a new digital watermarking method, called Multi-channel Watermarking Technique (MCWT), for the printed images. It embeds a hidden pattern into the original exhibited one in the multiple color channels and prints the watermarked results on the real paper. Then, the designed optical lens can extract directly the embedded pattern without the need of any complicate computation. Some experiments were performed. The experimental results show that the embedded image should be hidden in both cyan and magenta channels with the 15-30% size of the dot area. Meanwhile, these dots in the different channels are shifted along their screening angles.