get_alpha.m

用matlab实现的JPEG算法

% retourne la valeur de alpha ou plutot l'indice correspondant
% alp = [0.5 0.75 1 1.5 2]
%
% indice_alpha = get_alpha(Mat)
% ***********************************************************
function [indice_alpha,variation] = get_alpha(FID,M_coef) 

[N,M]= size(M_coef) ;
M_coef = reshape(M_coef,N*M,1);
M_coef = double(M_coef) ;

moy = mean(M_coef);
m_max = max(M_coef) ;
variation =std(M_coef,1); %/(2^10) 
KI = (sum((M_coef-moy).^4))/(variation^4);


indice_alpha = KI ;

indice_alpha = 1 ;

if KI<= 3024 , indice_alpha = 2 ; end ;
if KI<= 57.9 , indice_alpha = 3 ; end ;
if KI<= 12.00, indice_alpha = 4 ; end ;
if KI<= 3.762, indice_alpha = 5 ; end ;
if KI<= 2.658, indice_alpha = 6 ; end ;

fprintf(FID,'m_xi=%10g max=%g dv_xi %10g  Ki= %10g  i = %3g \n',moy,m_max,variation,KI,indice_alpha) ;