Abstract:

Block selection is a key strategy to improve the performance of pixel value ordering based reversible data hiding.By preferentially embedding data into blocks with a smaller fluctuation at first,better imperceptibility is able to be achieved.However,the accuracy of existing methods to calculate the fluctuation value is limited by the block size,shape and the selected predictor,so it is particularly important to design a calculation method that can be used under different block sizes,shapes and types of predictors.For large blocks or those irregular in shape,if the spatial position correlation of pixels used in the expansion is weak,even though the corresponding block is small in fluctuation,invalid shifting is still able to be introduced in the actual embedding process.To deal with this problem,we first propose an improved definition of fluctuation to consider the consistency of context pixels in horizontal,vertical,and bi-diagonal directions simultaneously.Once the consistency of adjacent pixels in the local neighborhood is determined,we further calculate the overall consistency of neighboring pixels in each direction,which improves the accuracy of block selection.Second,we consider the Chebyshev distance between the maximum value and the second maximum value,and that between the minimum value and the second minimum value,and reduce the invalid shift by subtracting the maximum or minimum pixel expansion.Experimental results show that our proposed scheme is able to achieve a better imperceptibility.

Key words: reversible data hiding, pixel-value-ordering, block selection, fluctuation value calculation, chebyshev distance