Horizontal pairwise reversible watermarking

The best results for very low embedding capacity reported so far are provided by a pairwise reversible watermarking scheme that uses paired embedding with rhombus prediction and context smoothness control. Since the horizontal (or vertical) adjacent pixels are more correlated than the diagonal ones, this paper proposes such a pairing for reversible watermarking. The rhombus prediction should be modified in order to match the horizontal/vertical pairing. An improved measure of the context smoothness is also introduced. The proposed horizontal pairing based reversible watermarking scheme outperforms the state of the art diagonal pairing one. Experimental results for standard graylevel test images are provided.