Resizing, Rotating, & Aligning Layers
Resizing a Layer
If you wish to resize a layer but want to keep the proportions within the layer the same then use Layer ▸ Rotate and Transform ▸ Scale and Rotate (⌘⇧T). Once you bring up this option, the inspector palette will display a scale percentage. You can change the percentage by manually typing in what you want, or you can hover over any corner of the layer and outward facing arrows will appear. Click and drag the cursor towards the inside of the layer to make it smaller, and to the outside to make it larger.
Under Layer ▸ Rotate and Transform you will also find Free Transform and Perspective Transform. Read transforming layers for more information on these options.
Rotating a Layer
You can easily rotate a single layer in your image in 90º increments by selecting Layer ▸ Rotate and Transform ▸ Rotate Layer 90o Clockwise (or Counter-Clockwise). If you want more control over the angle of rotation use Layer ▸ Rotate and Transform ▸ Scale and Rotate (⌘⇧T).
Unlike the other rotate commands, Scale Transform and Rotate allows you to set the layer at any angle in the canvas. Place your cursor outside the layer on the canvas and a rotating arrow icon will appear. Click and drag your cursor until you achieve your desired rotation.
You can manually type in the rotation values you want as well. Click on the angle field to enter your exact number or use the angle wheel.
Once you are finished rotating, double-click on the layer to release it or click 'Transform' in the palette.
Flipping a Layer & Offset and Wrap Layer
Layers can be flipped horizontally or vertically by selecting Layer ▸ Rotate and Transform ▸ Flip Layer Horizontal or Flip Layer Vertical. This will flip the individual layer on either the 'x' or the 'y' axis.
The offset and wrap layer menu item is useful for making seamless tiles. To learn more about this, read 'Creating a Seamless Tile'.
Multiple layers can be aligned with one another. Select the layers you want to align in the layers list. To select multiple layers you can either hold down the command key while you click on the layers, or hold down the shift key to select all the layers within a range. Go to Layer ▸ Rotate and Transform ▸ Align and select the function you wish to perform. Hold down the option key when you bring up the Align menu to show further options for aligning layers to the canvas.