parameters explanations for:
PCA(float **star,int Nstar,int Mp,double **basef,double **coff)

star : the image are arranged in Nstar*Mp matrix
Nstar :the number of inputed stars
Mp :Mp=nx*ny; nx,ny is the x and y pixel numbers
basef : output principal components (Nstar*Mp)
coff : the coefficient matrix arranged in Nstar*Nstar