flac --replay-gain

I have FLAC files that I would like to re-encode with --replay-gain.  I have my Flac's organized in Artist/Album folders, so I should have no problem getting an album gain/peak per album.

Do I need to first de-code the flac's to wav files and then "flac --replay-gain *.wav", or can this be accomplished by going to each Album directory and "flac -f --replay-gain *.flac"?