Determine if UIImageView has been rotated

If you just want to tell if the image has been rotated using an affine transform, as your question implies, you can do this:

if (CGAffineTransformIsIdentity(photoView.transform)) { 
    // not rotated
    ...
} else {
    // rotated
    ...
}

If you want to check for a particular rotation, do this:

CGAffineTransform t = CGAffineTransformMakeRotation(M_PI);
if (CGAffineTransformEqualToTransform(photoView.transform, t)) {
    // rotated by M_PI
    ...
}

Note that the above two solutions only work if you are not applying OTHER affine transforms to the view at the same time as the rotation transforms. If you are also applying other transforms, perhaps you are better off just tracking the rotation state in a variable.