I was trying to rotate images on the Mac, and was getting annoyed at the apparent lack of functionality to do so. In Windows, you could rotate images in Explorer and in Windows Preview after you’ve opened up the file. On Mac OSX, the Preview app doesn’t come with the “rotate” buttons visible by default. What you need to do is to right-click on the Preview menubar (like in the screenshot), and select “Customise Toolbar”. There, you’ll find the elusive “rotate” button. Drag it on to your toolbar, and you should see it there. Now, you’ll be able to rotate images in Preview by clicking on that button!
If you’re a keyboard-kinda person, the keyboard shortcuts for rotating images are:
Apple + L or Apple + R