linear discriminant analysis image code

hello

i have LFW dataset, it contains the faces of 5751 persons (only faces) and the total number of faces is 13233; i make them in in mat file (in 1*13233 cell )

my goal now is to reduce dimensionality of this mat file. and i have questions :

1-till now, i'm right in this proccess or no ?! if no give me the rights ideas .

2- how perform LDA for images ? code if exist ^_^ .