String bitmap get url path

Hi, I need to get the url path and play in the string for an impression.

Code:
string address = "00:00:00:00:00:;
MobilePrinter mobilePrinter = new MobilePrinter(address);
mobilePrinter.Connect();
Uri uri = new Uri("http://web.com.br/img/image_example.jpg");

//error //How to put correct code here
string bitmap = Android.Graphics.Bitmap + uri;

        mobilePrinter.PrintImage(bitmap);
        mobilePrinter.Close();

Thanks...