Data hiding by Exploiting Modification Direction technique using optimal pixel grouping

Zhang and Wang proposed the Exploiting Modification Direction (EMD) in 2006. The pixels in the image were grouped into n pixels per group. A pixel in each group is modified one gray scale value at most to hide a secret digit in a (2n+1)-ary notational system. In this paper, we proposed an optimized EMD method by analyzing the relationship between n and payload. The study involves using known payload on EMD to ascertain the least distortion result to begin the actual hiding process. Comparison results showed that the PSNR of optimized EMD embedding is significantly higher than OPAP and LSB by at least 3 dBs.