Do you want a lightweight apps to re-size your whole images ?
just fire-up your terminal, and enter this command :
kurogane:~ stev$ sips -Z 1024 *
that will re-size all your images in current folder, so make sure you have a backup. 😀
actually, sips can do a lot of things… just enter below command :
kurogane:~ stev$ sips –helpProperties
or you can check here