Previously, the image would not try to stay centered; furthermore,
on mobile devices, it was impossible to zoom images without dropping
them at a slightly off rotation. This bothered me enough that I've
clamped images to the center of the screen (as long as they aren't
zoomed larger than the screen) and snapped rotations to 45-degree
increments (with a nice animation to boot).
Log: on wm like sway, it will cover the whole screen, and I cannot get
the file save dialog, then the program will stay there, I must kill it,
so I think hide it is better, because after, it will be closed
