The Flip Horizontally command reverses the
active layer horizontally, that is, from left to right. It leaves the
dimensions of the layer and the pixel information unchanged.
You can access this command from the image menubar through
Layer → Transform → Flip Horizontally.
Figure 15.109. Applying “Flip Layer Horizontally”
Before applying the command
The layer after it has been flipped. It looks
as if the image has been reflected along the central
vertical axis of the layer.