| Summary: | 碩士 === 朝陽科技大學 === 資訊管理系碩士班 === 97 === 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.
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