中間對折策略之雙影像可逆式資訊隱藏方法

多數藏入方法在找到預測值後直接將機密訊息轉成十進制（或其他進制）的機密符號，與預測值（或像素）進行相加（或相減），完成嵌入動作。然而本研究發現，機密訊息也是影響影像品質很重要的因素，機密符號過大可能導致偽裝像素與原始像素差異較大，因此，本論文利用中間對折策略縮小機密符號的數值，將縮小後的機密符號透過平均法嵌入兩張偽裝影像當中，以維持影像品質。從實驗結果來看，本論文所提的方法與其他雙影像技術相比有相當不錯的表現，在相同藏量下，所提方法影像品質平均優於其他方法2 dB以上。再者，所提方法利用k值決定資訊藏入量，k值越大藏入訊息量越多。由實驗結果可以看出，在相同影像品質下，所提方法的藏入量較其他學者平均多約0.5 bpp以上。

Most information hiding schemes are focused on improving hiding mechanism. However, this paper found that the secret message is also an important factor which may effects the performance of the hiding technique. Large secret message many increase the distortion between the original pixel and the stego pixel. Therefore, this paper proposed a center folding strategy to reduce the secret message. The reduced secret message then averagely shared to two stego images. According the experimental results, the proposed scheme outperforms other methods. In the same hiding capacity, the image quality of the proposed scheme is 2 dB more than that of the other methods. Furthermore, the proposed scheme used k value to decide the hiding capacity. In the same image quality, the hiding capacity of the proposed scheme is higher than that of. the other methods.