These classes are UIImage categories written taken from Trevor's Bike Shed.

See author post for explanation: http:https://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/

It provides:

Extends the UIImage class to support resizing (optionally preserving the original aspect ratio), cropping, and generating thumbnails.

Extends the UIImage class to support adding rounded corners to an image.

Extends the UIImage class with helper methods for working with alpha layers (transparencies).