This is a demo project (for iPhone, but the code will work just fine on iPad too) showing two categories on UIImage, as described below.

This category lets you resize an arbitrary image to fit into an arbitrary size, using one of four resizing methods:

• Scale: scales the image proportionally to fit entirely into the required size.
• Crop: scales the image proportionally to completely fill the required size, cropping towards its center. This is the most useful method.
• Start: as for Crop, but crops towards the "start" of the image (the top or left, depending on relative aspect ratios).
• End: as for Crop, but crops towards the "end" of the image (the bottom or right, depending on relative aspect ratios).

This is very useful for caching on-screen-sized versions of images, and generating appropriate images for use on a Retina Display. The category will do the right thing based on the image's orientation metadata, and the scale factor of the device's main screen (i.e. it'll look sharp on high-resolution devices like an iPhone 4).

This category takes an image (presumably flat and solid-coloured, like a toolbar icon), and fills its non-transparent pixels with a given colour. You can optionally also specify a fractional opacity at which to composite the original image over the colour-filled region, to give a tinting effect.

This is very useful for generating multiple different-coloured versions of the same image, for example 'disabled' or 'highlighted' states of the same basic image, without having to make multiple different-coloured bitmap image files.

The license for the code is included with this project; it's basically a BSD license with attribution.

I can't answer any questions about how to use the code, but I always welcome emails telling me that you're using it or just saying thanks. I hope you find it useful!

Cheers,
Matt Legend Gemmell
http://mattgemmell.com/