Understanding Eigenface Face Recognition Algorithm Notations I have been reading the paper from Matthew A. Tusk and Alex Pentland

https://www.cs.ucsb.edu/~mturk/Papers/mturk-CVPR91.pdf

I got stuck in this part. I have a couple of questions.



Assume my images are 256 by 256.

1- What are G1,G2...Gm ? Row vectors? Column vectors? (1*65536) or (65536 * 1) ? Or are they 2D vectors (256*256)?

2- Then it says A = [ F1 F2 ... Fm] . Now I do not get this notation. Again A is what ? A matrix of matrices? or just a huge column/row vector?

Thanks
G1, G2... Gm are column vectors of length 65536.  The matrix A has columns that are the principal components.