Reversible Data Hiding Using Histogram Shifting in Small Blocks

This paper proposes a new approach based on the Histogram Shifting Algorithm (HSA) to reversible data hiding in bitmap image. The embedding is not carried out in the whole image but in small blocks in order to enhance the capacity. Firstly, the blocks are classified, and then, coding methods specific to each type of block are designed. Secondly, some blocks become unavailable for a second time embedding after the first one, while others are naturally unavailable. So as to separate these two kinds of blocks from each other, the status of blocks are defined, and a scheme of reserving blocks for taking identification information is proposed. Thirdly, the overall procedure of data embedding, extracting and image recovering are summarized. Test results on well-known images demonstrate the effectiveness of the new approach. The new method increases the total capacity of reversible data hiding to 1-4 times of the conventional method, and surprisingly, it also improves the PSNR value at the same time.