數位半色調變圖影像浮水印

Abstract

數位時代的快速發展，使文件資訊的傳遞更加便利及迅速，但也衍生出非法複製、盜印等問題，為了辨別文件真假，人們開始重視文件的防偽功能。以實體影像浮水印為例，目前具有變圖影像效果之浮水印隱藏效果不佳、隱藏資訊也較為固定單調及易於複製，且解密的方式也較為不便。結合以上問題，若以數位浮水印結合柱狀透鏡之變圖影像，可以增加浮水印之多樣化，並達到防偽效果，透過不同角度觀看柱狀透鏡讓解密更為方便。本研究結合數位浮水印與柱狀透鏡之變圖影像，製作由不同張數變圖原始影像組合而成之數位半色調變圖影像浮水印，於正常觀看下無法辨識，覆蓋柱狀透鏡解密後，即可得到隱藏之圖像，並經由不同角度觀看柱狀透鏡能得到變圖影像之效果。加密流程則需先設計多張二階化變圖原始影像之遮罩為素材，分別以數位半色調過網技術製成加密浮水印，再將加密浮水印分割成柱狀，交錯組合成數位半色調之變圖影像浮水印。經數位模擬解密後進行正確率評估，輸出於實體文件，覆蓋柱狀透鏡進行解密並觀察效果。經實驗結果，本研究可成功製作以兩張及三張原始圖製成數位半色調變圖影像浮水印，並加值應用於文創明信片產品。With the rapid growth of information technology, the transmission and processing of information have been greatly accelerated. However, it has also led to problems such as illegal copying, pirating, etc. In order to authenticate the information on the security documents, researchers have begun to pay attention to the anti-counterfeiting technologies. With regard to digital watermark for the document example, the current hidden figuration has a poor image-switching effect. The hidden image is mundane, fixed and easy to imitate and the way of decoding is inconvenient. Based on the above problems, using the digital watermark with image-switching effect can achieve higher level of security effect, decode message by sliding the lenticular lens, and make it more convenient to use. The objective of this study is to create the digital watermark with image-switching watermark by digital halftoning technique with different numbers of the image-switching images. Decoding by the lenticular lens shows the hidden images and has an image-switching effect by sliding the lenticular lens. The method of encoding processes is first carried out by selecting different number of images to be the masks of watermarks. The masks are then used to design the watermarks by digital halftoning technique. The digital watermarks have been processed with image-switching watermark through image interlacing and regrouping. The digital simulation of the decoding and the recognition rate of watermark extraction have been implemented before output. Then the printed document is decoded by the lenticular lens and compares with the results of digital simulation. The result of this study has been successfully achieved using two and three hidden images to create the digital watermark with image-switching watermark. This study has been produced the add-valued postcard.