www.gusucode.com > Diabetic retinopathy > enhance_composite_dc_sigma.m
function Y =enhance_composite_dc_sigma(C,beta,maxDC,k) [h w d]=size(C); Y=C; X=C(:,:,1); U=C(:,:,2); V=C(:,:,3); % compute s.d by summing of normailised AC coefficinets. xdc=X(1,1)/8; variance=0; for i=1:8 for j=1:8 variance=variance+(X(i,j)*X(i,j))/64; end end variance=variance-xdc*xdc; sigma=sqrt(variance); nxdc=xdc/maxDC; enxdc=nxdc*(2-beta*nxdc); exdc=enxdc*maxDC; factor=exdc/xdc; if(factor>255/(xdc+k*sigma)) factor=255/(xdc+k*sigma); end if(factor<1) factor=1; end udc=U(1,1)/8-128; vdc=V(1,1)/8-128; eudc=factor*udc+128; evdc=factor*vdc+128; U=factor*U; V=factor*V; U(1,1)=eudc*8; V(1,1)=evdc*8; Y(:,:,1)=factor*X; Y(:,:,2)=U; Y(:,:,3)=V; return