Reversible watermarking based on generalized histogram shifting

This paper proposes a generalization of the well-known histogram shifting method for reversible watermarking. Binary watermark source is converted into a non-binary source that produces symbols from an alphabet of n (n>;2) symbols. A technique similar to that of generalized least significant bit (GLSB) is used to transform watermark; therefore, arithmetic coder is used in source coding stage. In order to embed data, histogram is shifted between border points according to the number of symbols that are being created by generalized watermark source and pixels that take the value of border point are modified like in the original histogram shifting method with the only difference that modification is no longer limited to only {0,1} but to {0,1,..., n-1}. It is shown analytically and verified through experimental results that this generalization can increase the flexibility of histogram shifting technique and permit the embedder to better adapt itself to the embedding problem.