Color image steganography scheme using gray invariant in AMBTC compression domain

In this paper, a novel color image steganography scheme using gray invariant in AMBTC compression domain is proposed. Unlike the conventional schemes, the proposed scheme embeds the secret data into a compressed color image while keeping gray pixel values intact. First, the proposed scheme partitions each color component (R, G, B) of a cover image into non-overlapping blocks with the same size and calculates the standard deviation and variance of the sub-block. Next, two least complex blocks having minimum variance out of the three-color blocks are compressed using dynamic AMBTC compression and the secret data is embedded into bit-planes of smooth compressed blocks. To keep the gray pixel values invariant, the pixel values of the most complex color block are adjusted according to the pixel intensity on the reconstructed compressed blocks. Therefore, the proposed scheme can reduce the size of the color image and embed a significant amount of data while keeping gray pixel values intact. The main advantages of the proposed scheme are: (1) reduces the required bandwidth for image transmission due to AMBTC compression, (2) preserves gray values of the original cover image, which helps in many applications such as black and white printing, fingerprint scanning and so on, (3) uses color plane blocks selectively for data hiding which makes the proposed scheme more robust, and (4) uses a dynamic AMBTC compression for least complex color planes, which helps in achieving good PSNR and high embedding capacity.