Reversible watermark using difference expansion of triplets

A new reversible watermarking algorithm based on the difference expansion of colored images has been developed. Since the watermark is completely reversible, the original image can be recovered exactly. The algorithm uses spatial and spectral triplets of pixels to hide pairs of bits, which allows the algorithm to hide a large amount of data. A spatial triplet is any three pixel values selected from the same spectral component, while a spectral triplet is any three pixel values selected from different spectral components. The algorithm is recursively applied to the rows and columns of the spectral components of the image and across all spectral components to maximize the hiding capacity. Simulation results show that the hiding capacity of the algorithm is very high and the resulting distortion is low.