There are plenty of photo cropping applications for iOS. Here's a new wrinkle that caught my eye. The app is called AntiCrop, and it's a US $0.99 universal iPad app that does the opposite of cropping a photo. It actually adds new data to the top and sides of an image, allowing you to reframe something that didn't come out right in the first place.
AntiCrop is kind of the reverse of Photoshop's content-aware fill. Content-aware fill allows you to take something out of a photo by blending in nearby pixels. Anti-crop works at the edges, and pretty accurately gives you new data that doesn't look especially fake or blended in after-the-fact.
The application is pretty easy to operate. You load a photo in from your existing photo library, and by dragging on handles at the edge of the photo you reframe the aspect ratio and watch the new pixels fill-in. It's pretty incredible to watch, and most of the time, it works exceedingly well.
You can run into problems if you drag the borders too far away and force the program to fill in pixels that obviously repeat data that is in your image. I only saw that behavior a few times, and when it appeared I was really extending the frame quite a bit, which is asking a lot of the algorithms the program uses.
Another use is to straighten a tilted horizon. Normally we have to crop to fix the edges of the tilted photo, but anti-crop just puts in new data at the edges and the problem is solved. Of course you can do the reverse, to tilt a horizon that was originally shot level.
This is a very clever application that can make sloppily taken pictures come back to life. Like anything, it can be overused, and of course the technology has limitations, but I like AntiCrop for its innovative thinking and low price.
AntiCrop is perfect for when you are on vacation and want to fix some less than ideal photos. I can think of a lot of other uses, too.
The app also runs on an iPhone or a 3rd or 4th generation iPod touch; it requires iOS 3.1 or later. To get a good idea how the app works, take a look at this tutorial video and check my gallery examples below.