get_ri.m

用matlab实现的JPEG算法

% ----------------------------------------------------
% fonction permettant de calculer Ri en fonction de :
%		Lagrangian
%		pond閞ation i
%		Alpha i
%		sigma i
% ----------------------------------------------------

function [S_Ri] = get_Ri(FID,Flra,Fpond,Fsigma)

Fv = log10(Flra  / Fpond) ; % log(EQM)

% ******  Fsigma >= 40 *******
if Fsigma > 40
 
   S_Ri = 10^(-0.3714*Fv + 0.7) ;

end ; % if > 40 --------------

% *****   10 < Fsigma < 40 ***
if (Fsigma >10)&(Fsigma<=40)
 if Fv < 0.6

   S_Ri = 10^(-0.1+ (0.4*(1+ ((-Fv + 0.6)/0.4  )^5   )^(1/5)));
 else
   S_Ri = 10^(-0.0875*Fv+0.275);
 end;
end ;

% *****  Fsigma < 10 *********
if Fsigma <= 10
 if Fv < 0.4
   S_Ri = 10^(-0.1+ (0.4*(1+ ((-Fv + 0.6)/0.4  )^5   )^(1/5)));
 else
   S_Ri = 10^(-0.1*Fv+0.36);
 end;
end;

% *****************************