EDIT: the answer I would suggest would be to wait for Picasso 2.3, or fork their github now, where you can actually get at a BitmapDrawable.
One approach I've found so far is that you can load images into a Target object, create a custom drawable from the bitmap that way, then set the drawable into the ImageView, where it'll draw without creating a new bitmap.
This approach sort of sucks for a few reasons though:
1) You have to manage Target objects. These are weak-referenced (thankfully), so you have to keep track of them yourself. Ick. Memory leaks ahoy.
2) When you get the callback, you had better check to make sure the state of the world is still relevant to the picture, which is part of what you want to avoid by using picasso.
In short, there are a few things that seem to prevent a better solution.
1) Picasso wraps bitmaps in PicassoDrawables. This means you you have to handle arbitrary drawables in your custom imageView (if you go that route), or special case for this class. 2) PicassoDrawable doesn't expose the source bitmap, so you have to convert the drawable to a bitmap (requires creating a new bitmap, afaict). 3) There's no bitmap -> drawable transform function (see #1 for why, most likely).
Would love to hear if there's something I'm missing, or someone has come up with a better solution. Right now my best plan is to either do the Target management proposed above, or fork the picasso repo, change PicassoDrawable to have a public accessor for the underlying bitmap, and do the conversion into a custom drawable that way in my imageView.