Flip Image

A flip is a mirror, and it is lossless

Flipping reverses the image along an axis, so every pixel moves to a mirrored position and none is altered. It is fully lossless and reversible: flip again along the same axis and the original is restored exactly. That makes it one of the few edits with no quality consideration whatsoever, which is worth knowing because several other adjustments in this category do have a cost.

• Horizontal flip: mirrors left to right, like looking in a mirror.
• Vertical flip: mirrors top to bottom, sometimes called upside down.
• Both are lossless and exactly reversible.
• No re-encoding quality is lost unless the save format is lossy.

The selfie mirroring problem

A front camera shows a preview that is already mirrored, and most phone cameras save that mirrored preview. The result is that a selfie saved from a front camera reads backwards, which looks wrong to everyone except the person who took it, because they are used to seeing themselves in a mirror. Flipping horizontally corrects it. This is by far the most common reason anyone flips an image, and it is a correction rather than a creative choice.

• Front camera selfies are usually saved mirrored and read backwards.
• A horizontal flip fixes the text and the overall scene.
• A back camera photo is not mirrored, so it should not be flipped.
• If text in a selfie photo reads backwards, a horizontal flip is the fix.

NoteA selfie that looks fine to the photographer and odd to everyone else almost always needs a horizontal flip.

When flipping text is the wrong fix

Flipping a whole image to correct backwards text mirrors the text itself, which is just as unreadable. The distinction is whether the text was mirrored as part of the scene, which happens with a mirrored preview, or whether the image contains no text and the problem is simply the scene being reversed. If you need text in the correct reading order, re-editing or re-typing it is the fix. A flip fixes a mirrored photograph, not a mirrored document.

• Mirrored photo with no text: flip horizontally, which is correct.
• Mirrored scene where text should read forwards: flipping mirrors the text too.
• A document that arrived mirrored needs re-editing, not a flip.
• Decorative mirrored text is sometimes intentional. Check before correcting it.

Vertical flips and how they are used

A vertical flip is much less common than a horizontal one and is usually used to correct an image that is upside down, which is often the same thing as a 180 degree rotation, so rotation is usually the better tool. It also has a specific use in photography, where flipping an image vertically while mirroring it horizontally is how a mirrored selfie is corrected without turning it upside down, since the two operations together equal a 180 degree rotation. It is also occasionally used to move a horizon to the opposite side for a compositing task.

• Upside down image: a 180 degree rotation is usually the cleaner tool.
• Correcting a mirrored selfie: a horizontal flip is what is needed.
• Compositing: a vertical flip can place an element on the opposite side.
• Stacking two images: matching orientations often needs a vertical flip.