Getting datastore Info through an API

How does one get image data (image url, image info) from datastore through an api?

Is there a tutorial or a project that lets you upload imag开发者_如何学Goes like FotoRatan but also has an api which can be used to get the image and image info from another website?

Here is an example how to store and serve files (maybe images) using Blobstore: http://code.google.com/appengine/docs/java/blobstore/overview.html#Uploading_a_Blob

You should also look at Picasa Web Albums Data API