求PSNR

functionf = WPSNR(A,B,varargin)

% ThisfunctioncomputesWPSNR(weightedpeaksignal - to - noiseratio)between
% twoimages.Theanswer is in decibels(dB).
%
% Usingcontrastsensitivityfunction(CSF)toweightspatialfrequency
% oferrorimage.
%
% Using:WPSNR(A,B)
%
% WrittenbyRuizhenLiu,http: // www.assuredigit.com

if A == B
error( ' Imagesareidentical:PSNRhasinfinitevaluelilizong ' )
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( ' inputmatricesmusthavevaluesintheinterval[0,1] ' )
end

e = A - B;
if nargin < 3
fc = csf; % filtercoefficientsofCSF
else
fc = varargin ... {1} ;
end
ew = filter2(fc,e); % filteringerrorwithCSF

decibels = 20 * log10( 1 / (sqrt(mean(mean(ew. ^ 2 )))));
% disp(sprintf( ' WPSNR=+%5.2fdB ' ,decibels))
f = decibels;

%=============
functionfc = csf()
%=============
% ProgramtocomputeCSF
% ComputecontrastsensitivityfunctionofHVS
%
% Output:fc --- filtercoefficientsofCSF
%
% Reference:
% MakotoMiyahara
% " ObjectivePictureQualityScale(PQS)forImageCoding "
% IEEETrans.onComm.,Vol 46 ,No. 9 , 1998 .
%
% WrittenbyRuizhenLiu,http: // www.assuredigit.com

% computefrequencyresponsematrix
Fmat = csfmat;

% Plotfrequencyresponse
% mesh(Fmat);pause

% compute 2 - Dfiltercoefficient using FSAMP2
fc = fsamp2(Fmat);
% mesh(fc)

%===================
functionFmat = csfmat()
%===================
% ComputeCSFfrequencyresponsematrix
%
% Calledbyfunctioncsf.m
%
% Frequencyrange:therangoffrequencyseemstobe:
% w = pi = ( 2 * pi * f) / 60
% f = 60 * w / ( 2 * pi),about 21.2
%
min_f = - 20 ;
max_f = 20 ;
step_f = 1 ;
u = min_f:step_f:max_f;
v = min_f:step_f:max_f;
n = length(u);
Z = zeros(n);
for i = 1 :n
for j = 1 :n
Z(i,j) = csffun(u(i),v(j)); % callingfunctioncsffun
end
end
Fmat = Z;


%========================
functionSa = csffun(u,v)
%========================
% ContrastSensitivityFunction in spatialfrequency
% Thisfilecomputethespatialfrequencyweightingoferrors
%
% Reference:
% MakotoMiyahara
% " ObjectivePictureQualityScale(PQS)forImageCoding "
% IEEETrans.onComm.,Vol 46 ,No. 9 , 1998 .
%
% Input:u --- horizontalspatialfrequencies
% v --- verticalspatialfrequencies
%
% Output:frequencyresponse
%
% WrittenbyRuizhenLiu,http: // www.assuredigit.com

% ComputeSa -- spatialfrequencyresponse
% symsSwsigmafuv
sigma = 2 ;
f = sqrt(u. * u + v. * v);
w = 2 * pi * f / 60 ;
Sw = 1.5 * exp( - sigma ^ 2 * w ^ 2 / 2 ) - exp( - 2 * sigma ^ 2 * w ^ 2 / 2 );

% Modification in Highfrequency
sita = atan(v. / (u + eps));
bita = 8 ;
f0 = 11.13 ;
w0 = 2 * pi * f0 / 60 ;
Ow = ( 1 + exp(bita * (w - w0)) * (cos( 2 * sita)) ^ 4 ) / ( 1 + exp(bita * (w - w0)));

% Computefinalresponse
Sa = Sw * Ow;