An Improved Bidirectional Shift-Based Reversible Data Hiding Scheme Using Double-Way Prediction Strategy

Algorithm 2

Pseudocode of embedding process 2.

	Input: first-stage stego image I1, secret sj and that are, respectively, one bit of the secret message S, and threshold
	Output: stego image
	for each pixel, I1 (i, j), except for the pixel in the first column and the first row of I1
	Scan in the reverse raster scan order from the pixel in the bottom right corner of I1;
	Calculate the prediction error of I1 (i, j) as with equations (3) and (4);
	Generate of I1 and PK^∗ = 2 × ,  = 2 × PK^∗;
	Compute zero bins and denote them as Z^∗rn^∗ and Z^∗lm^∗;
	/left expanding and shifting/
	if
	Δbin^∗ (i, j) =  −  −sj;
	elseif
	Δbin^∗ (i, j) = −PK^∗ + m^∗, where ;
	else
	Δbin^∗ (i, j) = 0;
	endif;
	(i, j) = I1 (i, j) + Δbin^∗ (i, j);
	end;
	/finish left and begin right expanding and shifting/
	for each pixel (i, j)
	=  (i, j)  =  + Δbin^∗ (i, j);
	if
	=  + SH^∗ + PK^∗ + ;
	elseif  > SH^∗
	=  − n^∗, where , ;
	else
	= 0;
	endif;
	=  (i, j) + ;
	=  + Δbin^∗ (i, j) + ;
	end;
	/finish embedding process 2/