Enhancing the Robustness of Visual Degradation Based HAM Reversible Data Hiding

Purposely visual degradation of image quality is a newfangled idea in the area of Histogram Association Mapped (HAM) reversible data hiding. Such scheme first divides the color scale, i.e., 0-255, into some partitions by the range, difference of minimum and maximum value of a block. Next, the histogram of a block resided to a partition, original partition, is moved, e.g., shifted, to another partition named reflective partition. First, an association between the original and reflected partition are defined by a chunk of secret message and then the translations of the bins of the histogram of the original partition to the reflective partition are performed to complete the message concealment. In such schemes, the blocks are classified as Reflective Block (RB) and Non-Reflective Block (NRB) based on whether the range is less than 127 or not. Experimentally, it is observed that most of the RB blocks occupy the portion of two partitions which introduce a dilemma in defining original partition as well as associating and hence translating bins. Again, at NRB the range of occupied bins in the histogram of a block is enough longer than the available bins where to reflect. Therefore, the policy of associations and then translations of bins of histogram may force the pixel values to exceed the extremes of gray scale which is indeed impossible. Solutions to these issues are not presented by any literature so far we have studied. Besides, the side information database that is practiced to assist in decoding at receiver is made longer by storing bundle of information and sometimes it becomes near or more than both the secret data and size of image. Resolutions to these stated observations are presented in this article. Experimental results justify the necessity of mitigating these observations.