% =============================================================================
% Math 336 - Image Processing - Laboratory 2
%
% A Matlab function for stenographic recovery of a hidden image in the 
% the bit planes of another image using the original primary image as a 
% reference. Note that this function assumes the 4 most significant bit planes
% of the "hidden" image are in the 4 least significant 
%
% Marty Kandes
% Department of Physics
% San Diego State University
% Fall 2008
% -----------------------------------------------------------------------------
function [H] = recover(OIMAGE,PIMAGE)
F = imread(OIMAGE);
G = imread(PIMAGE);
F = double(F);
G = double(G);
F0 = (mod(F,2)); 
F1 = (mod(floor(F/2),2));
F2 = (mod(floor(F/4),2)); 
F3 = (mod(floor(F/8),2));
F4 = (mod(floor(F/16),2)); 
F5 = (mod(floor(F/32),2));
F6 = (mod(floor(F/64),2)); 
F7 = (mod(floor(F/128),2));
G0 = (mod(G,2)); 
G1 = (mod(floor(G/2),2));
G2 = (mod(floor(G/4),2)); 
G3 = (mod(floor(G/8),2));
G4 = (mod(floor(G/16),2)); 
G5 = (mod(floor(G/32),2));
G6 = (mod(floor(G/64),2)); 
G7 = (mod(floor(G/128),2));
G7 = xor(F0,G0);
G6 = xor(F1,G1);
G5 = xor(F2,G2);
G4 = xor(F3,G3);
H = uint8(2*(2*(2*(2*(2*(2*(2*G7+G6)+G5)+G4)))));
end