'brew info libgd'

gd: stable 2.1.0, HEAD
http://libgd.bitbucket.org/
/usr/local/Cellar/gd/2.1.0 (33 files, 1.7M) *
  Built from source with: --with-freetype, --with-libvpx, --with-libtiff
From: https://github.com/mxcl/homebrew/commits/master/Library/Formula/gd.rb
==> Dependencies
Recommended: libpng, jpeg
Optional: freetype, libtiff, libvpx