[pmelendez]

From the notes of your link:

"drawImage() will ignore all EXIF metadata in images, including the Orientation. This behavior is espacially troublesome on iOS devices. You should detect the Orientation yourself and use rotate() to make it right. "

If the origin of the image is the client and you got the client side resize wrong, then you might introduce artifacts when trying to fix it on the server because the data loss. Also if clients are mobile, you might like to optimize the battery of clients instead of computing time on the server.

[Matt3o12_]

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.

[Xeoncross]

Even several years ago there were libraries on github that accounted for iOS defects. However, that aside, just skip the resize on iOS and send as-is. The server still has to verify the result anyway.