數位影像半色調技術與浮水印隱藏

目前大多數黑白印表機使用網點技術來模擬灰階色彩，事實上是由大量黑白兩種顏色的點所組成，使用人類眼睛無法細查的點，經過人眼後會產生灰色的錯覺，這就是所謂的半色調技術。半色調技術應用非常廣泛，例如噴墨印表機、傳真機、報紙、雜誌、漫畫印刷等，大都使用半色調圖像來輸出。本論文探討有序抖動、誤差擴散、點擴散等半色調技術，探討各種把灰階圖片轉成半色調圖片的技術並比較其優缺點。資訊加密是網路發達時代所常探討的一種技術，把浮水印隱藏於圖片中藉此把隱密資訊傳遞也是一種資訊加密的方式，由於半色調圖片容量小於灰階圖片和彩色圖片，故使用半色調圖片可減少傳遞資訊所需的時間。本論文第三章將介紹用隨機誤差擴散、雜訊平衡誤差擴散等方法，藉由改變門檻值及誤差值把浮水印隱藏於經誤差擴散的半色調圖片中，最後我們提出利用改變門檻值把浮水印隱藏於經有序抖動圖片的方法，我們也提出使用改變點擴散的擴散順序藉此隱藏浮水印的方法。

關鍵字

半色調；浮水印

並列摘要

Most black and white printers use screentone technology to simulate the gray color. In fact, it composes of a large number of two-toned black and white dots. Since the human eyes can not scrutinize these dots, after the human eye it will produce the illusion of gray, which is the so-called halftone technique. Examples include inkjet printers, fax machines, newspapers, magazines, and comic books printing. Most of them use halftone images as outputs. This thesis first reviews order dither, error diffusion, dot diffusion and other existing halftoning techniques. We will explore techniques to convert the gray-scale image into a halftone image and compare their advantages and disadvantages. Information encryption is often discussed in this network age. A technology to hide watermark in an image to transmit the secrete watermark information is also an information encryption method. Because the information amount is less for halftone images than for grayscale and color images, transmission of halftone images can reduce the time required. Chapter 3 will explore the use of stochastic error diffusion, noise-balanced error diffusion, and other methods to hide the watermark in the error diffused halftone pictures. Finally, we propose new methods to hide watermarks in two halftone images. Specifically, we propose to use threshold changes to hide watermarks in order dither halftone images. We also propose to change error diffusing orders of the dot diffusion halftoning technique to hide the watermarks.

並列關鍵字

watermark ； halftone

參考文獻

[2] 郭景明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 國立台灣大學電信工程學研究所博士論文民國91年2月

[5] M. S. Fu and O. C. Au, “Data hiding in halftone images by stochastic error diffusion,” in Proc. IEEE Int. Conf. Acoustics, Speech and Signal Processing, pp. 477–484, May 2000.

[6] J. F. Jarvis, C. N. Judice, and W. H. Ninke, “A survey of techniques for the display of continuous-tone pictures on bilevel displays,” Comput.Graph. Image Process., vol. 5, pp. 13–40, 1976.

[10] D. E. Knuth, “Digital halftones by dot diffusion,” ACM Trans. Graph., vol. 6, pp. 245–273, Oct. 1987.

[11] S. C. Pei and J. M. Guo "Data hiding in halftone images with noise-balanced error diffusion", IEEE Signal Process. Lett. , vol. 10, pp. 349, 2003.

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數位影像半色調技術與浮水印隱藏

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