混合網點數位浮水印輸出控制研究

Abstract

混合網點數位浮水印技術，應用調幅網點及調頻網點兩種不同形式的網點，將浮水印藏入半色調影像中，藉由不同形式的網點對複印或是掃描等數位複製設備的取樣差異來進行解碼。實體影像受限於輸出設備因素，只能以半色調的形式來呈現，半色調影像經由人類視覺的模糊化積分後，產生連續調影像的感覺。數位浮水印是在數位影像中藏入標記、圖案、號碼等等資訊，本研究針對混合網點數位浮水印輸出成實體浮水印，考量輸出設備特性，控制網點的大小及疏密程度，使數位浮水印輸出後，得到最佳的隱蔽性，且經由複印機等解碼設備偵測後，可以得到隱藏的資訊。

The objective of this thesis is to hide watermark with hybrid halftone dots in a printed halftone image. Two different halftone dots, Amplitude Modulation (AM) and Frequency Modulation (FM), are use to design the digital watermark. The output parameters should be carefully controlled to obtain printed image with hidden digital watermark. As the printed image is copied or scanned, the hidden watermark is shown because of the under-sampling of the FM halftone dots. The outcome of this research has many potential applications in security printing, such as ID, legal document, checks, stamps, and currency.