Transforming Selection Marquees in Photoshop

To transform just the selection marquee without affecting the underlying pixels, make your desired selection and then choose Select➪Transform Selection. Photoshop doesn’t have a submenu with individual transformations to choose from. Instead, you must apply the transformations like you do with the Free Transform command: by using the keyboard shortcuts. You can also enter values in the Options bar to transform numerically, or you can access the context menu. To move the selection marquee and the bounding box, simply drag inside the marquee or nudge it by using the keyboard arrow keys. Transforming selections is particularly handy when you’re trying to select elliptical objects. It is often hard to get the selection precise the first time around, so applying a transformation is often necessary.

Distorting selected pixels with Free Transform
The Transform menu isn’t the only way to distort selected pixels. A much more efficient way is to use the Free Transform command, also found on the Edit menu. Like the Transform command, the Free Transform command surrounds your selection with a bounding box. Within the bounding box, you can scale, rotate, skew, distort, or apply perspective without having to choose the individual distortions. You just have to use the right keyboard shortcuts. To scale and rotate, use the same method as the Transform commands. Here’s the scoop on the rest:
- Skew: Ctrl+Shift+drag (Ô+Shift+drag on the Mac) on a side handle
- Distort: Ctrl+drag (Ô+drag on the Mac) on any handle.
- Perspective: Ctrl+Shift+Alt+drag (Ô+Shift+Option+drag on the Mac) on a corner handle.

Unfortunately, if you want to apply a flip or rotate by degree while free transforming, you need to use the Transform submenu. While the bounding box is surrounding your selection, you can also access a context menu that offers all the transform options. Right-click (Control+click on the Mac) on your canvas to access this handy shortcut.