| 摘要: | 在資訊隱藏的領域中，隱藏量(hiding capacity)是一項重要的議題，因此有一些學者提出結合影像壓縮技術的資訊隱藏方法，這類的方法會將秘密影像先行壓縮，再將壓縮後的影像藏入偽裝媒體中，在這些方法中最常被使用的影像壓縮技術為向量量化(vector quantization, VQ)。最近Shie, Lin, and Jiang (2010)提出將秘密影像利用向量量化壓縮，並將壓縮後產生的索引表藏入編碼簿中，因此僅需將編碼簿傳給接收端，即可還原秘密影像。Shie等人的方法可提高藏密量與降低傳輸量，但其方法會破壞編碼簿，使得還原之秘密影像品質降低。本研究的目的便在於改善Shie等人的方法，在同時保有該方法的優勢下，盡可能地提昇還原的秘密影像品質。本研究利用差分演化法改變編碼字的排列，可使索引表藏入編碼簿時，對編碼簿的改變量最小，使得還原的秘密影像品質比Shie等人的方法更好。
In the field of information hiding, the hidden capacity is an important issue, so there are some scholars proposed the video compression technology of the information hiding scheme, such method will compress the secret image first, then the compressed image is embed into the stego media, in these methods most commonly used video compression technology is the vector quantization (VQ). Recently Shie, Lin, and Jiang (2010) proposed a secret image compression using vector quantization, and the compressed index table generated is embedded into the codebook, so just transmit the codebook to the receiver, and receiver can restore the secret image. Shie et al.'s method can be increased the hiding capacity and improved to reduce the Transmission capacity, but the method will destroy the codebook, resulting the degradation of the quality of the restored secret image. The purpose of this scheme is to improve Shie et al.'s method, at the same time retain the advantages of this method, as much as possible to enhance the quality of the restored secret image. The proposed scheme, the differential evolution method will be utilized to change the arrangement of codeword, it will result the smallest amount of change for the codebook when the index table is embedded into the codebook, and the quality of the restored secret image will better than the Shie et al.'s method. |
