Minima is designed to quickly and easily shrink images taken by the camera on your iOS device, and works incredibly well. Because of the naturally very large file size of most images on the iOS camera, it can become a space issue quickly--Minima fixes this problem, automatically, as you take new photos.
To shrink an image in Minima, all you need to do is open it. Tap the image in your library to open it and it will be instantly resized, according to the settings. There are five options here--mini, midi, maxi, and either iPhone or iPad. You can set it to resize, automatically, or you can choose to have it ask you each time, a good option if you want to avoid filling your library with accidentally resized images. You can also share your images after resizing or save them to your camera roll, automatically. All of this works seamlessly and allows you to shrink the size of your photo library quickly, either to save space or for sharing.
Minima is a good app, but practically requires the $0.99 paid upgrade to remove watermarks placed on your photos. That said, if you need a solid photo app to take smaller photos or resize what you already have, Minima does it quickly and works without any issues in the background of your phone.