Emgu CV is a cross platform .Net wrapper to the OpenCV image processing library. Allowing OpenCV functions to be called from .NET compatible languages such as C#, VB, VC++, IronPython etc. The wrapper can be compiled by Visual Studio, Xamarin Studio and Unity, it can run on Windows, Linux, Mac OS X, iOS, Android and Windows Phone.
Build instructions can be found here: http://www.emgu.com/wiki/index.php/Download_And_Installation#Building_from_Git
Open Source releases can be found here: https://sourceforge.net/projects/emgucv/files/emgucv/