資訊隱藏技術應用於半色調影像之研究

A Study of Information Hiding Based on Halftone Images

郭晉廷(Jin-ting Kuo)

指導教授 ： 曾顯文

朝陽科技大學/資訊學院/資訊管理系/碩士(2008年)

摘要

在現今網際網路普及的時代，造就了使用者利用便利與快速的網路環境，來傳遞彼此間的數位資訊。然而在一般安全機制的網路環境中，傳輸的資料很容易被截取，為了避免重要資料在網路傳輸中遭任意複製、竄改及偽造，故資訊隱藏技術便應運而生。目前的許多文獻都是以灰階或彩色影像為研究的方向，然而在日常生活中半色調影像廣泛使用在書籍、傳真、影印等等非彩色的影像資料上。我們希望能在半色調影像裡嵌入一些有用的資訊，像是將浮水印嵌入在影像中做版權的保護，或者是做影像是否被破壞的偵測。在本篇論文裡我們將提出兩個資訊隱藏方法，第一個方法是針對半色調影像的可逆式資訊隱藏技術，所謂可逆式資訊隱藏即是影像在取出嵌入資訊後可以回復到原始狀態。我們將Ni等學者所提之直方圖修改技術，結合格雷碼編碼的概念進一步應用在半色調影像上，達到在嵌入大量資訊的同時，還可以兼顧到影像品質，不至於被破壞的太嚴重。第二個方法是一個不可逆的資訊隱藏技術，此方法利用重疊區塊來嵌入秘密資訊，並結合Fu學者所提之DHSPT(Data Hiding by Smart Pair Toggling)概念，使我們可獲得更高的藏入量，並且影像品質將不會有明顯失真。

關鍵字

DHSPT ； 半色調影像 ； 格雷碼 ； 可逆式資訊隱藏 ； 直方圖修改

並列摘要

With the great advance of technology and the well popularization of Internet, people always transmit digital data on Internet. Although it is very convenient, the transmission of data could be intercepted by anyone in this environment. To avoid the important data to be copied, garbled or faked, data hiding (steganography) appeared. In current literature of data hiding techniques, most are applied to grayscale and color images. In the other side, halftone images also have great applications, such as the printing of books, newspapers, magazines and computer printers. It is often desirable to embed data into the halftone images as value-added content, or for copyright control and authentication purposes. In this research, we proposed two data hiding techniques for halftone image. One of the methods is a reversible data hiding scheme. The image can be restored to original image after the data is extracted. We modified Ni''s method of histogram and combined the concept of Gray Code to the hiding method. This method not only has high hiding capacity, but also can generate stego-images with good quality. The second method is not a reversible data hiding method, but it can provide a large hiding capacity. It is a great improvement of Fu’s DHSPT scheme. The overlapping blocks are used to embed the secret data and the stego-images can be generated without noticeable distortion.

並列關鍵字

Reversible hiding ； Halftone image ； Histogram modification ； Gray code ； DHSPT

參考文獻

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