Use the Flip command to reverse an image along its horizontal axis—the on top becomes the bottom and vice versa. Use the Mirror command to reverse the image along its vertical axis—the left side becomes the right and vice versa.
Note: To flip or mirror all layers in an image, make them all part of the same layer group.
To flip a selection, layer, or image:
Choose Image > Flip or press Ctrl + I. Flipping a selection converts it into a floating selection, leaving the original layer unchanged.
To mirror a selection, layer, or image:
Choose Image > Mirror or press Ctrl + M. Mirroring a selection converts it into a floating selection, leaving the original layer unchanged.
Scaling and Transforming Images