Originally Posted by twowheels
No, it's not. Jpeg artifacts would *NOT* give the very clear squared of stairstep pattern across the top.
JPG artifacts are frequently apparent in 8x8 blocks (or tiles) similar to what's seen above. This would be most apparent in blocks that contain widely different values (like the border of the screen or areas around text).
I'm agnostic on this matter so far. Is there a link to the original image? I didn't see if at first glance.