Get byte array of image in photo library

For periods when network connectivity is not available I want to save the path details of photo taken (using the Media Plugin by James Montemagno) and then try to send the image later. I've created a LocalFileProvider class as a platform specific implementation to get the image file but for iOS I end up with an album path like:
"assets-library://asset/asset.JPG?id=3108374C-74DC-40BD-9A09-DF93C0FD2122&ext=JPG"

How do I construct a path that could then be used with the File.ReadAllBytes(filePath); to be able to get a byte array to send the saved image.

I haven't tested on Android yet but will the scenario be similar for accessing a file in the standard location?

Thanks