function Signature=LPDBkSignature(Imagery,T) 
%use principal component of coorelation matrix to obtain the background signature.

[m,n,l]=size(Imagery);
Imagery2D=reshape(Imagery,m*n,l);
Imagery2D2=Imagery2D';

Correlation=0;
 for i=1:m*n
      Temp=Imagery2D2(:,i)*Imagery2D2(:,i)';
      Correlation=Correlation+Temp;
end

Correlation=Correlation/(m*n);
[V,D] = eig(Correlation) ;

for i=1:l
    EigenValue(i)=D(i,i);
end

EigenValueSum=sum(EigenValue);
EigenValueWeigeht=EigenValue/EigenValueSum;

EigenWeightSum=0;
for i=1:l
    Temp=EigenValueWeigeht(l-i+1);
    EigenWeightSum=EigenWeightSum+Temp;
    if EigenWeightSum>T
          break;    
    end
end

Signature=V(:,l:(-1):l-i+1);
% P=OrthCompletProjection(U);%消弱背景的投影算子
% ImagerySuppressB=P*Imagery2D2;
% ImagerySuppressBMin=min(min(ImagerySuppressB));
% ImagerySuppressB1=ImagerySuppressB-ImagerySuppressBMin;