Reversible data hiding in VQ index table with lossless coding and adaptive switching mechanism

In recent years, reversible data hiding (RDH) has attracted extensive attention from the academia. Besides RDH for uncompressed images, RDH for compressed images with satisfactory embedding performance is also important due to the universal use of image compression. In this paper, a RDH scheme for the encoded Vector Quantization (VQ) index table through the Improved Searching Order Coding (ISOC) is proposed. Original image is first compressed with a sorted VQ codebook and further losslessly encoded by the ISOC technique to produce an index table, in which all indices are categorized into three types, i.e., SOC type, Relative Addressing (RA) type and VQ type, based on the relationship between the index and its neighborhood. Each of the first two types of indices is adaptively switched or unchanged according to the current secret bit to be embedded, and the third type of indices isn't used to embed secret data. Experimental results show that, our scheme can embed secret data into 78.396% and 78.377% of all image blocks when VQ codebook sizes equal 256 and 1024, respectively. Compared with the reported schemes, our scheme can achieve higher hiding capacity with lower bit rate and extension degree of index table.