Some questions about attachment_fu and image_science

It took me some hours, but i finally managed to have attachment_fu
running with image_science - that's an achievement for me :slight_smile: I have a
few questions about how to use it properly:

In the attachment_fu readme, it says
:resize_to # Used by RMagick to resize images.
                      # Pass either an array of width/height, or a
geometry string.

What happens here when you have image_science instead of rmagick? can
i give image_science exactly the same options and the same geometry
strings? and where can i find some more info about these geometry

What is a proper way of implementing an image into another model? For
example, i'd like to have something like user.avatar. should i put
has_one :avatar into the user-model? (and the has_attachment and
validates_as_attachment in the avatar-model?)