The image is already held locally on the client PC and it is an Air application. The image is not embedded, it is in the Application Storage directory.
I have seen this question: How can i get a BitmapData object out of a File object from a local jpeg file in AIR? but it uses URLRequest which I don’t think is what I need because the file is local.
Using file.url will give you a url you can use with a URLRequest even though the file is local.