Corrections to “JPEG Anti-Forensics With Improved Tradeoff Between Forensic Undetectability and Image Quality” [Aug 14 1211-1226]
Wei Fan, Kai Wang, François Cayre, Zhang Xiong · IEEE Transactions on Information Forensics and Security · 2016
In the above paper [1, p. 1215], it was assumed that [1, eq. (8)] was a convex optimization problem. However,$C(X)$(see [1, eq. (6)]) is in general not convex, since it is an absolute value of the difference between two convex functions. Indeed, the proposed cost function is non-convex. By using the subgradient method with the chosen steps, however, we can get a quite good solution (probably a local minimum) that has a sufficiently low cost function value. This makes the proposed algorithm work sufficiently well, as demonstrated by the experimental results.