數位半色調技術之深入探究、改進及其與數位浮水印技術之混成應用

Thorough Investigation, Improvement, and Data Hiding Watermarking in Digital Halftone Images

郭景明(Jing-Ming Guo)

指導教授 ： 貝蘇章

國立臺灣大學/電機資訊學院/電信工程學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.00804

摘要

另外由於數位文件、多媒體處理工具及網際網路間的媒體交流不斷激增，導致數位資料在著作權及傳播上的控管不易，因此目前普遍採用傳統的類比式浮水印觀念提出新一代的數位浮水印技術來解決數位媒體著作權的保護、所有權的追蹤、文件原創性認定及資料的隱藏。這類的技術所需注意的問題包括強健性(資料遭破壞後仍有能力驗證)、隱藏資料容量、資料嵌入後之影像品質、隱藏資料之不可移除性及隱藏資料的解碼辨識率。目前已有許多如何在半色調影像內嵌入數位浮水印的相關技術發表，這類的技術可用於具有安全性質的文件列印處理，例如身份證或鈔票，且避免遭受不合法的複製利用，例如將文件經過掃瞄還原成數位資料形式再予以傳播。
數位浮水印可被設計成脆弱性或強健性。脆弱性浮水印可被一般影像處理輕易破壞，因此較適用於文件是否遭受竄改的偵測與驗證。強健性浮水印用於抵抗惡意或非故意性的攻擊，因此較適用於著作權的保護。一般來說，資料隱藏法(data hiding)屬於脆弱性，數位浮水印技術(digital watermarking)則屬於強健性。在本論文中我們提出一系列數位半色調技術結合資料隱藏法及數位浮水印的混成技術，實驗證明這些方法可在強健性、容量、影像品質、解碼辨識率上得到不錯的結果。

關鍵字

數位浮水印技術 ； 數位半色調技術

並列摘要

Output devices such as halftone printers and palette-based displays are ca-pable of producing only a limited number of colors, whereas the human eye can distinguish around 10 million colors under optimal viewing conditions. Due to the low pass nature of human visual system. The eye perceives only a local spa-tial average of the spots produced by a printing device and is relatively insensi-tive to errors made in high frequencies in an image. Halftoning algorithms therefore aim to preserve these local averages while forcing the errors between the continuous tone image and the halftone image to high frequency regions. Existing halftoning techniques can be broadly classified as ordered dither, error diffusion, and iteration-based halftoning techniques.
The evolution of computer and printer technologies, as well as economics, has been driving the current research. Some issues arise and need to be solved. For example, photographic printed quality, dot gain problem, and halftoning speed.
In this dissertation, first, we propose an iteration-based halftoning, named LMS-halftoning to achieve high quality outputs, which was proved with higher PSNR than error diffusion. Second, a perfect printer model used to overcome the dot gain problem is also proposed here. Finally, a new progress coding scheme applied for order dither images is also included in this work.
The proliferation of digital documents, multimedia processing tools, and the worldwide availability of Internet access have created an ideal medium for copyright fraud and uncontrollable distribution of multimedia content. To deal with this problem, conventional analogue watermarking technology has been adapted to digital media as a tool to achieve copyright protection, ownership trace, authentication, or information hiding. The major issues include robustness, capacity, imperceptible, undeletable, undeletable, and unambiguous. Currently, numerous methods using halftones to embed watermarks have been studied. These techniques can be used for printing security documents such as ID card, currency as well as confidential documents, and prevent from illegal duplication and forgery by further scanning these documents to digital forms.
Some watermarks are fragile and some are robust. Fragile watermarks are designed to be broken easily by common image processing operations and are good for tampering detection and authentication. Robust watermarks are de-signed to survive hostile and/or unintentional attack and are good for copyright control. Generally speaking, data hiding techniques are fragile, and watemark-ing are robust. In this dissertation, we propose several watermarking and data hiding in halftone images that address all the issues described above.

並列關鍵字

digital watermarking ； digital halftoning

參考文獻

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