Because of iOS sandboxing rules it's not possible to read data directly such URL. IOW your image does not belong to your application (it's not kept in it's directory).
What you can do is use the ALAssetRepresentation
to get the image (and the options you want) data and then POST that data to your web server.
There's a few ways to do so but in general you can get CGImage
from ALAssetRepresentation
, which can be used to create an UIImage
which can be converted to an NSData
(representing a PNG or JPEG) and then you can get a System.IO.Stream
usable to POST.