PROGRESSIVE REVERSIBLE DATA HIDING BY SYMMETRICAL HISTOGRAM EXPANSION WITH PIECEWISE-LINEAR HAAR TRANSFORM *

In this paper, we present a progressive reversible data hiding technique by symmetrical histogram expansion in the transform domain of Piecewise-Linear Haar (PLHaar). Data are embedded into the PLHaar coefficients of images progressively from the pivotal bin of a histogram of PLHaar coefficients to both sides of the pivot symmetrically. With PLHaar, no overflow or underflow occurs to the pixel values, and our data hiding method achieves the highest embedding capacity with PSNR around 50dB compared to the previous methods in the literature. The method can also be applied to artificial images with an exactly flat histogram, which is impossible for a method to hide data in the spatial domain. The progressiveness of the proposed method also enables a rough but automatic capacity-PSNR control. The effectiveness of our method is demonstrated with a number of experiments. Index Terms — Reversible data hiding, symmetrical histogram expansion, PLHaar, capacity-PSNR control