Adobe has released Photoshop for iPad. You can try it for a 30-day free trial, and after that it requires a subscription to Creative Cloud that costs US$9.99/mo.
This first version focuses on core compositing and retouching tools designed to work best on the iPad with Apple Pencil and touch. And we’re just getting started. For future versions, we’re looking at enhancing our tools used for brushes, masks, refining edges, and selecting smart subjects. Plus, we want to make it easier to access your brushes and fonts in Creative Cloud.
Early reviews of the app say it’s a bit rough around the edges, but download it to see for yourself. App Store: Free (Offers In-App Purchases)