Even if sending binary data with JSON is a no go.. here are the steps you need to do.
1. read the image data to a byte array (byte)
2. convert this array to base64 encoded string (you need a lib or class from the internet that does this for you)
3. add the string to a json object
4. send that object to its destination
Due to the base64 encoding the filesize of the image will increase to 133% while transporting.. on the server
side when its decodec back to a byte array its the same as before of course.