Afterlight (nee Afterglow) is a powerful image editor for iOS that was updated recently to include iPad support. iPhone photographers will find lots to like about this now universal and still 99-cent app.
As with most image-editing apps, Afterlight lets you snap a shot or load one from your Camera Roll or photo stream. In settings, you can tweak such things as starting the app in camera mode, saving the original image, and autofinalizing filters and textures, which means you won't have to confirm the use of a filter or texture each time you choose one and move to another editing tool (you can add multiple filters and textures).
After loading a photo, you'll see six edit buttons along the bottom of the screen. The left-most button is an undo button, which lets you undo each change you've made. Next to it is the adjustments button, which features 15 different tools -- exposure, brightness, tones, temperature, and so on -- to tweak your image. Each tool features a slider that lets you fine-tune the intensity of the effect.
The next button contains 40 filters, each of which features a slider to adjust its effect. The filters are split into two groups. There are 27 original filters (five of which are locked until you like the app on Facebook), and then there are 13 guest filters created by Instagram users.
The film button contains three groups of textures. There are 13 dusty filters, 31 light leak textures, and for a 99-cent in-app purchase you can unlock the third group, the Instant film pack that contains another 22 textures plus seven frames. For each texture, you can adjust its intensity and orientation.
The fifth button from the left lets you crop, flip, rotate, and straighten your image, while the right-most button lets you add a frame. Some frames are in the shape of letters or numbers, which I was hoping at first would let you add text to an image, but such functionality is lacking.
Afterlight is easy to work with on both the iPhone and iPad, but in addition to giving you more space with which to work, the iPad app lets you work in either portrait or landscape mode; with the iPhone, you're stuck with portrait mode unfortunately.
When you have your image edited just so, tap the Done button in the upper-right corner to access the share and save screen. You can save it in one of three resolutions and share among the usual suspects, including Instagram.