綠雜訊半色調技術於浮水印之研究

['資訊科技的蓬勃發展，文件資料複印也日趨便利快速且精密，但也造成文件資料的偽造情況層出不窮；⼤量⽂件遭⾮法複製導致著作權與智慧財產權受到侵犯，因⽽顯現出印刷防偽技術對智慧財產保護之重要性。⽬前半⾊調影像加密技術中，以FM (Frequency Modulation)網點及AM (Amplitude Modulation)網點為主軸，但FM網點的網點擴張(Dot gain)問題較⼤⽽AM網點細部的表現較差；因此有學者提出綠雜訊半⾊調技術，改善FM及AM網點缺點，降低網點擴張情形及保留邊緣細緻度；由過去研究中發現⽬前綠雜訊技術多以製作半⾊調影像為主，未發現利⽤綠雜訊半⾊調技術藏⼊實體浮⽔印之研究。因此本研究之⽬的以綠雜訊半⾊調演算法為基礎，⽅法為改變演算法中種⼦形成⽅式利⽤不同網點尺⼨製作浮⽔印及底紋，並以HVS (Human visual system)評估其隱藏效果，尋找出最佳浮⽔印濃度及尺⼨，製作防偽⽂件，使⽂件經複印後⽴即顯現隱藏之浮水印。結果顯⽰，此綠雜訊半⾊調技術所製作之防偽⽂件，經由複印機複印及⼿機拍照將影像上傳⾄電腦進⾏程式解密後，能有效地顯現所隱藏之浮⽔印，達到防偽效果，保護⽂件之版權。 ']

關鍵字

數位半色調；數位浮水印；綠雜訊半色調

並列摘要

['Owning to the vigorous development of information technology, file and documents duplicating is becoming more convenient and precise. However, it has also caused endless cases of falsification; massive data has been illegally duplicated which has seriously infringed one’s intellectual property rights. All the facts above reveal the importance of anti-counterfeiting for intellectual property protection. The current halftone image encryption technology to FM (Frequency Modulation) dots and AM (Amplitude Modulation) dots are viewed as the protagonists, but FM dots resulting in greater Dot gain problem and its performance on details of the AM dots is inferior; therefore some scholars have issued green noise halftone techniques which can reduce Dot gain and remain the high resolution on the edges. Discussion from the reference found that the current green noise technology for the production of halftone image on based, Unused green noise halftone encryption produced a watermark. Therefore, the purpose of this study is to change the way the formation of seed algorithm with different sized dots watermark and shading by using the green noise halftone algorithm as the base. And to assess its encryption effect by HVS, in order to find out the best concentration and dimension of watermark to produce security documents, which reveal the hidden watermark after duplicating. The results showed that the documents with this green noise halftone encryption technology can effectively reveal the hidden watermark and to use mobile phone take a picture to upload image to computer for the decryption program, which achieve the effect of security and protect the copyright. ']