FlipPictureA PictureEditor.com tool

Reference

Reference pages on mirroring

Three pages, each written because one specific misunderstanding about reflection costs people an afternoon.

None of these teaches the controls. The bench has five of them and they explain themselves in use. What the bench cannot do while you are standing at it is settle the question that sent you to it — whether the picture in front of you was mirrored or turned, whether the press on the other end of the file will reverse it again, whether the face you are looking at is the one the sensor actually recorded. Each page takes one of those, follows it as far as the arithmetic or the hardware allows, and stops at the point where it would have to start guessing.

The three of them

  1. Mirrored or turned5 min

    The determinant test, stated plainly: why a double reflection lands on exactly the grid a half turn lands on, and why no composition of flips will ever produce a quarter turn.

  2. Printing a mirrored image6 min

    Four transfer processes, sorted by whether the press reverses the artwork for you, plus the one print-dialogue setting that silently undoes the reflection you just saved.

  3. Why your selfie is reversed4 min

    The front camera shows a live mirror and writes the unmirrored frame to storage, which is why the face you approved is not the face anybody else has been looking at.

The gaps

Why there are only three

A page gets written here when it can be checked. Two more are owed and neither is started: reflecting a JPEG on its encoder blocks, which avoids the re-compression the bench currently pays on every save, and reflecting an animation frame by frame rather than flattening it to its first. Both are named as limits on the tool pages, because a limit you can read is worth more than a page that restates it without solving it. Neither becomes a reference page until there is something here that would survive being measured.

Rotation is the one subject that will never get a page of its own here, although it is discussed in the first of the three. Turning a picture is a different transform with a different determinant, different behaviour on the orientation flag and a different cost on a JPEG, and this site does not perform it. Writing a full guide to an operation the site refuses to run would be a page that exists to be found rather than to be useful.

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