| Summary: | 碩士 === 銘傳大學 === 資訊管理研究所 === 91 === Data hiding in images is a type of technique that embeds secret messages or watermark information in digital images. In this dissertation, we proposed three novel data hiding methods during the processes of images halftoning for gray images.
The first approach we proposed is using two dithering matrices to code secret data bit-stream. The stego-image originated by this method has good visual quality. In the second approach, we use many images which include four classes to train the result of dithering with two dithering matrices to product the template-probability-rank table. When we dither a gray-level image, we embed data with the relationship of rank values in the template-probability-rank table between two resulting templates of dithering. The stego-image originated by this method has also good visual quality and the embedded data can be extracted out from the resulting stego-image without referencing the original image. In the third approach, another method of data hiding in halftone images is developed, which integrates the data hiding operation into the error diffusion process with two different error diffusion filters. Due to the different results of pixel value originated with two error diffusion after thresholding, we can embed data into halftone images. The halftone image which was embedded a large amount of data has also good visual quality similar to one originated with an error diffusion filter. Experimental results show that the proposed approaches are feasible and effective.
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