Thanks for the update, I'm sorry that I couldn't reply you further, I was quite occupied by work recently. Anyway I've tested portrait mode, it displayed in proper size and orientation now.

However, when viewing the picture in the built-in gallery, I found that portrait photos tend to looked fuzzy and poorly rendered like badly resized thumbnail. No such problem for landscape photos though. Everything looks fine though using the Gallery

This leads me to a subsequent question, why do you build your own gallery instead of using the existing one? Is it because the gallery is closed?