Although iPhoto for iOS isn't quite as robust as its OS X counterpart, it's a very capable image editor—and it can do a few cool tricks you simply can't do on your Mac.
Straighten your photos
iPhoto for iOS allows you to straighten your photos in a few smart ways. The first is by auto-detecting a strong horizon line. Open iPhoto, choose a photo and then tap Edit. Now tap the Crop & Straighten icon in the bottom left. If the photo displays a white line across it with icons at either end, then that means a horizon line has been detected. To proceed with straightening, simply tap the arrow icon at the right.
Unfortunately, iPhoto can't always detect a horizon line and that means you'll have to make the adjustment yourself. The Crop & Straighten mode places a dial under your photo, and you can straighten your photo simply by dragging the dial left or right. A grid overlaid on your photo as you turn the dial, lets you straighten with visual cues in your photo.
What happens when your photo has no visual cues, but still feels off-kilter? iPhoto for iOS has one more strategy to assist you, and it's a lot of fun. Choose a photo you want to straighten and then hold the iPad or iPhone up in front of you. Now tap the dial. iPhoto then calls on the gyroscope in your device to help you straighten the image. Simply tilt the iPad or iPhone to the left and right; as you do, you'll notice that the photo remains upright. It's helpful to tilt your head as you tilt the device so that you have a better sense of the final crop. Once you're happy with the position of the photo, tap anywhere on the screen to lock it in.
Apply and tweak effects
iPhoto for iOS has many more effects than its desktop counterpart. Open iPhoto, choose a photo and then tap Edit. Now tap the Effects icon in the lower left. A swatch of possible effects will then pop into view. There are two sets of effects that are particularly impressive: Vintage and Ink Effects. Choosing Vintage presents you with a set of six effects, and each of them gives your photo a warm, antique feel. Once you've chosen an effect that you like, you can adjust the size and placement of the vignette by pinching the photo and dragging your finger across it. And if you don't like the vignette, you can toggle it on and off by tapping the vignette icon at the right (tap the yellow question mark on the top, if you're not sure where it is).
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