How to make the avatars work like this?

Hey,

I am trying to make my avatars work as follows and have tried few plugins and couple of pieces of code but without any luck:

1) If user has a local avatar (on my site) then it should be displayed as an avatar – without making a call to gravatar domain

2) if there is no local gravatar then users gravatar should be used in comments – of course this will make call to gravatar domain

3) if user doesn’t have a gravatar account then the default image should be loaded from local domain – without making a call to gravatar image

I searched for “avatar” in plugins and tried almost every plugin that seem to do something similar but none of them did exactly this.

I really appreciate your input