ImageProcessor
Wrapper around System.Drawing for the processing of image files
... but developing it has taken thousands of hours of my time and a large part of my sanity. If you feel like dropping me a few precious pounds (there’s no obligation) it would go a great way to ensure that I can afford to take the time to continue to improve the library. It's fast, extensible, easy to use, comes bundled with some great features and is fully open source.