So I had a friend send me some photos via WhatsApp messenger (iPhone to iPhone) and only just realised that the WhatsApp app lowers the resolution of your images before transmitting them to the other user.
I ain't even mad at WhatsApp as it is completely reasonable that they do this to make the whole image transfer more efficient, but it isn't exactly general knowledge that they do this. I only realised this when I transferred the image to my computer and noticed the image file was low res for an iPhone image.
This is pretty important for the photographers out there who have started using their smartphones more. Lesson here is don't use WhatsApp to transfer / transmit images if you need the original image in full quality.
The original image above (captured on an iPhone 6 Plus) was 3,189 x 2,387 and was shrunk down to a puny 1,252 x 937 (down to about 39% of the original size).
Here is another example of an image going from 2,448 x 3,264 to 960 x 1,280:
Who knows which other apps out there compresses files like this.. My friend sent it to me via the iPhones native Messages app and the files weren't compressed.