Clustering Steganographic Modification Directions for Color Components

It is conventionally assumed that steganographic schemes for gray-scale images can be directly applied to color images by embedding messages independently in different color channels. However, the correlation among color channels may be disturbed and it is unclear how to preserve the channel correlation so as to increase empirical security. In this paper, we propose a strategy called CMD-C (clustering modification directions for color components). The basic idea of the strategy is to change different color components from the same pixel location towards a positive or negative direction consistently. To implement the strategy, we decompose an image into several sub-images in which segmented hidden message bits are successively embedded. The embedding costs of a sub-image are computed by considering the correlation both within and among color channels. Experimental results show that the proposed CMD-C strategy has made great improvement over conventional methods in resisting state-of-the-art steganalytic methods.