混合網點浮水印之交界區域處理技術

Boundary processing on the watermark by hybrid halftone dots

高彥翔(Kao Yen-Hsiang)

指導教授 ： 王希俊

國立臺灣師範大學/科技與工程學院/圖文傳播學系/碩士(2016年)

https://doi.org/10.6345/NTNU202203916

摘要

['隨著科技的興盛，偽造設備也日漸發達，其中以紙張的偽造最為簡便，隨處可得的複印機即可快速又清晰的複印，因此衍生出智慧財產權問題。為了保護智慧財產權，許多學者致力於紙張防偽技術研究，最普遍的技術是浮水印技術，其中，混合網點數位浮水印是以調幅（Amplitude Modulation, AM）網點製作浮水印及調頻（Frequency Modulation, FM）網點製作底紋，藉由複印機無法同時複印兩種不同尺寸網點的特性製作浮水印，但此浮水印在交界處會因為網點尺寸不同產生模糊的輪廓，且於近距離觀察時，人眼可直接觀察出此輪廓，降低浮水印的隱藏效果。
本研究目的為改善混合網點浮水印交界區域之問題，以網點尺寸漸變的方式模糊兩者的交界區域，且處理後的浮水印仍保有浮水印的防偽性質。本研究將設計交界區域漸變之演算法，交界區域從網點大的AM到FM，改為網點大AM到網點小的AM，再到FM，其中網點小的AM區域可分多次且網點尺寸變化幅度小，以此達到漸變的效果，並且以模擬人眼的HVS（Human Visual System）評估其隱藏效果。
實驗結果顯示，交界區域漸變演算法使得混合網點浮水印技術有更好的隱藏效果，未來可應用於紙張文件的防偽，藉此提高其隱藏效果。
']

關鍵字

浮水印技術 ； 混合網點 ； 漸變

並列摘要

["With the flourishing development of science and technology, duplicating equipment can make paper copy in an easy and convenient way. In order to protect creator's intellectual property rights, a large number of anti-counterfeiting technologies for paper have been developed, and the most commonly-used one is the digital watermarking technique. Halftone-based watermark is also an important research area for document security. Among them, watermark byhybrid halftone dots, which are formed by both amplitude modulation (AM) dots and frequency modulation (FM) dots was proposed. Because AM and FM have different sizes of dots, people will observe the watermark by a closer look at the document. In study,we design a boundary processing technique to make the boundary from bigger AM dots to smaller AM dots to FM dots. Then,using Human Visual System algorithm to evaluate the visibility of encrypted watermark in the boundary area. Results shows that, the boundary processing can effectively hide the watermark in certain range of observation. The boundary processing algorithm can be applied to document security, it can provide a better hidden watermark."]

並列關鍵字

watermarking ； hybrid dots ； gradual change

參考文獻

一、西文部分

Alasia, A.V. (1976). Process of coding indicia and product produced thereby, U. S. Patent No. 3937565. Whitestone, NY: U.S. Patent and Trademark Office.

Chen, Y.T. & Wang, H.C.(2002).A watermarking technique for print-and-scanned digital pictures with the modification of geometrical transformation.in proc. 15th Conference on Computer Vision, Graphics, and Image Processing, Shinchu, Taiwan

Chou, C.M., Wang, W.C., & Wang, H.C. (2006). Watermarking a holographic image on cd-r disks, in proc. 2006 Conference on Computer Vision, Graphics and Image Processing, pp. 804-811, Taoyuan, Taiwan.

Floyd, R. W., & Steinberg, L. (1976). An adaptive algorithm for spatial grayscale. Proceedings of Society for Information Display, 17(2), 75-77.