Adaptive Image Steganography with Mod-4 Embedding using Image Contrast

A new adaptive steganography method based on image contrast to improve the embedding capacity and imperceptibility of the stego images is presented. The method exploits the average difference between the gray level values of the pixels in 2x2 blocks of non-overlapping spatially and their mean gray level in order to select valid blocks for embedding. The method was tested on different gray scale images. Results show that our proposed approach provides larger embedding capacity, while being less detectable by steganalysis methods such as chi 2 attack and machine learning steganalysis systems, as compared to some well-known adaptive and non-adaptive steganography algorithms.