Display Fisherface after reducing dimensions using PCA

Hi,

I'm learning to implement the Fisherface algorithm using Matlab. I understand that to deal with the singularity issue of Sw, I can project Sb and Sw onto the PCA space of r dimensions, with r ≤ rank(Sw) and compute the Fisherfaces in this PCA space. If I set r = 1000, what are my Fisherfaces' dimensions, and how do I display them as images? Do I need to reconstruct them back to their original dimensions? If so, how do I do this?

Thank you.