The question now is, what drains more power, sending the image and resizing it before sending. If the user has a good WiFi or 4G connection, sending the file as it, should be quicker and more energy efficient. With a 2G or 3G connection, uploading a photograph can take significantly longer (1min on poor/average 3G, which means the antenna is working for that duration and draws a lot of battery). Converting it should not take more then a second. Furthermore, I would prefer using less data then using a tiny amount of battery.