The Picasa APIs enable you to create buttons users can install in the Picasa client user interface (see image below). Once installed, the button exports selected images from Picasa to another desktop application or web-based service.

The BlogThis! button in Picasa uses these APIs
Picasa offers two APIs:
Note - These APIs are used to export images from Picasa to other applications and web services. If you are interested in becoming a Picasa print partner, please contact us.