Zmarties

I've mentioned before that Picasa is one of the few Google offerings without a (published) API. However, although unpublished, there are a number of integration points with Picasa that form a sort of unofficial API.

Specifically, Picasa offers the following

• upload to a Web Album (new in the Picasa 2.5 beta version)
• upload to Joga (in the customized version of Picasa available at Joga.com)
• upload to Blogger

This uploading interface is undocumented, but has been reverse engineered by tabblo, who use it to offer a way to upload to the tabblo photo service direct from Picasa. They offer few clues as to how they did it, beyond this comment on a flickr forum, to the effect that

"we had to spend a couple of days reverse-engineering a complicated desktop application/server-based protocol, then more time debugging it, and as of late, more time bringing it up to date for the 2.5 release of Picasa."

Picasa has some other potentially useful integration points

• the oem.xml file is used by the Joga customized variant to supply the customization of the title bar
• Picasa 2.5 uses kml files to interact with Google Earth, with the communication in the reverse direction acomplished by Picasa acting as a web server
• Picasa also shows a webserver interface when you use the Ctrl-L shortcut, which gives a close approximation to the Picasa UI within a web browser
• Picasa Web Albums offer a "download to Picasa" link that works by using a url of the form "picasa://downloadfeed/?url=http%3A%2F%2Fpicasaweb.google.com%2Flh%2FrssAlbum" so Picasa must register a url handler for the "picasa://" protocol.

Whilst the above are all undocumented, there is documentation provided for another integration point. If you look in the web directory under your Picasa installation, there is a documentation directory, and within that is a index.html file which documents the Picasa Web Templating System. This describes the templating system used when doing an export as web page from Picasa. In addition, you can also export as xml, which provides another fairly easy way to extract data from the Picasa system, for use in other programs.

Labels: picasa