Flip an image

Flipping costs nothing in quality because it only reorders pixels — no interpolation happens, so the result is exactly as sharp as the original. Ticking both directions is the same as rotating 180°, which is occasionally the quicker way to think about it.

The usual reason people want this is a selfie. Front cameras show you a mirrored preview because that is what you are used to seeing, but most save the unmirrored version — so the photo looks subtly wrong to you and completely normal to everyone else. Flipping it horizontally gives you back the face you see in a mirror.

The one thing to check before flipping is text. Anything written in the image — a sign, a label, a watermark, a logo — becomes backwards, and it is easy to miss when the text is small or at the edge. Numbers on a clock face and vehicle registration plates are the classic ones people only notice after posting.

Worth knowing for the technical case: flipping is often used to double a training dataset for machine learning, and it is safe for most subjects and wrong for a few. Anything where handedness matters — text, road scenes in a country that drives on one side, medical images — is corrupted rather than augmented by a horizontal flip.