Learn how to use CIFilters in your code. Frist, try different filter parameters and review resulting image. After you achieve desired effect - export source code in Objective C.
CIFilter is a considerable part of Core Image network, but its often not clear what parameters to use to achieve desirable result. App provides the possibility to play with different filter parameters and review results based on sample images as well as images from your album. The resulting image could be saved, emailed or exported to notes. For each filter, code in Objective C could be reviewed and copy-pasted to your app.
Filters can be applied one over another to find the solution for desired image if it could not be achieved by one filter.
App can be used as a sophisticated photos enhancer/editor as it provides direct access to all filter parameters.