I was having a hard time converting a digital photo down to the correct 2″x2″ physical size. Then I found this article: take your own passport photos. At first, I was thinking “Tell me something I don’t know.” Then I saw the link to the State Department’s own online passport photo editor (photo tool). Perfect! Well, I’m still ugly in the photo, but they can only do so much.
On the subject of converting, this site seems good for converting various digital formats from one to the other: FreeConvert.com