.NET advanced GIF library
This repo is a fork of NGif-Animated-GIF-Encoder-for-NET by gOODiDEA.NET. He originally ported it from Java but it contained a few bugs and minor annoyances. This fork can animate GIFs frame by frame and supports writing to memory or file streams.
The original implementation also had bugs with transparency appearing as black as well as the last two pixels rendering as the wrong color, but these have been fixed.
See the original project here: http://www.codeproject.com/Articles/11505/NGif-Animated-GIF-Encoder-for-NET