Juxtaposer is a compositing tool that allows you to the take the best elements of one image and combine it with a second image to create a whole new scene. Pocket Pixels has been steadily updating the app since it launched in 2008 and has turned it into one of the best tools to combine two images into one.
For those who are not familiar with Juxtaposer, the app allows you to select a background image for your scene and a foreground image that overlays the background. You can remove parts of the foreground image, isolating only the small parts you want to overlay. For example, you can take a shot of someone in a barrel at Niagara Falls and quickly replace that person with your own smiling selfie.
What sets Juxtaposer apart from the competition is its suite of editing tools that make the app a delight to use. These carefully crafted options include a zoom box so you can precisely see what parts of your image you are erasing and adjustable paintbrush options that let you select the right size eraser for your image. Other useful editing tools include:
an unerase tool that allows you fix mistakes
a red mask mode to easily see the areas of the top photo that are being removed
a transparent mode that lets you precisely align the top image over the bottom image
a "move top" tool that lets you select the top image and adjust its size and location
a stamp tool that saves your edited top image for future use in other compositions
Another major advantage of Juxtaposer is its image correction tool that allows you to adjust the contrast, shadows, saturation, color temp and more. You can make these adjustments to the top image and background separately which is critical if you want your two composited images to match as perfectly as possible.
And last but not least is a new iPad version that allows you to combine your images in either landscape or portrait mode on the larger and more comfortable editing canvas of the iPad. The iPhone is great for quick composites, but the iPad is perfect for detailed compositions.
Juxtaposer is US$2.99 in the iOS App Store. It is a universal app and requires iOS 7.