%function f = WPSNR(A,B,varargin)
% This function computes WPSNR (weighted peak signal-to-noise ratio) between
% two images. The answer is in decibels (dB).
%
% Using contrast sensitivity function (CSF) to weight spatial frequency
% of error image.
%
% Using: WPSNR(A,B)
%
% Written by Ruizhen Liu, http://www.assuredigit.com
% read in the cover object
file_name='1.bmp';
A=imread(file_name);
% read in the message image
file_name='2.bmp';
B=imread(file_name);
A=double(A);
B=double(B);
A=A./255;
B=B./255;
if A == B
error('Images are identical: PSNR has infinite value')
end
max2_A = max(max(A));
max2_B = max(max(B));
min2_A = min(min(A));
min2_B = min(min(B));
if max2_A > 1 | max2_B > 1 | min2_A < 0 | min2_B < 0
error('input matrices must have values in the interval [0,1]')
end
e = A - B;
if nargin<3
fc = csf; % filter coefficients of CSF
else
fc = varargin{1};
end
ew = filter2(fc, e); % filtering error with CSF
decibels = 20*log10(1/(sqrt(mean(mean(ew.^2)))));
% disp(sprintf('WPSNR = +%5.2f dB',decibels))
f=decibels
