Uploading photos on LiveJournal

Hi All.

I want to write a simple utility (using Java) to upload pictures in LiveJournal Scrapbook directly from my PC (or, say, a cellphone???). I need some help to get started, i.e.

What documentation I should go through.
What APIs I can use.
The general method to accomplish what I intend to accomplish.

Just an outline would be enough; I will find out the rest.

Thanks.

Dexter.