Mirror or Flip Image

The front camera of a smartphone shows a mirrored image on screen during preview, because this is what users expect to see: it mirrors the experience of looking in a mirror. When the user takes the photo, most iOS systems save the image as seen on screen (mirrored), while most Android systems save the 'real' image (non-mirrored). This inconsistency causes confusion: on iOS the saved image is mirrored (as in the mirror), on Android the image is inverted compared to what was seen on screen. To get the desired orientation, horizontally flipping the photo after taking it corrects the result on any platform.

Flip and mirror are synonyms in image editing: they describe an axial reflection, not a rotation. Horizontal flip (left-right mirror) creates an image that is a reflection across the central vertical axis: what was on the left is now on the right and vice versa. Vertical flip (top-bottom mirror) reflects across the horizontal axis: what was on top is now on the bottom. Rotate is completely different: it turns the image a number of degrees around a central point, displacing all pixels angularly. Rotating 180° produces the same visual result as applying horizontal flip + vertical flip simultaneously.

In product photography for e-commerce there are established visual conventions: watches are generally photographed showing 10:10 (the classic position from watch ads, which frames the brand and creates visual symmetry). Shoes are almost always presented pointing to the right because in Western writing cultures the gaze moves left to right, and the object 'pointing in the direction of the gaze' is perceived as active and dynamic. Cars are typically presented showing the left (driver) side because culturally it is the most familiar side. Flipping a product image may be necessary to respect these conventions when the original photos have the wrong orientation.

Horizontal flip (left-right flip) is the most frequent type: it fixes selfies, adjusts object orientation, and is the standard 'mirror effect'. It is used in portrait photography to test whether a composition works better as a mirror image. Vertical flip (top-bottom flip) is less common in general photography but widely used in graphic designs: water reflections in photographic compositions, vertical symmetry effects, and correction of scanned images with the document face down. In UI design, vertically flipping an arrow icon (chevron) can reuse it as a variant in four orientations without creating new assets.

From a technical standpoint, flipping an image does not change its resolution or dimensions (it is the same pixels, just reorganized). However, it can affect the size of the compressed file. JPEG uses DCT (Discrete Cosine Transform) compression that analyzes 8×8 pixel blocks. A flipped image may have a different distribution of spatial frequencies that results in slightly different compression. The difference is generally less than 1-3%. PNG, being lossless, will compress differently if the pixel pattern changes (DEFLATE is sensitive to the direction of gradients). In practice, for most images, the file size change is imperceptible.