I found that SWT is available in CCV, an open-source Computer Vision Library:
http://libccv.org/doc/doc-swt/[
^].
You can download the source code and learn how it works, to write it in C# or make a translation.
Alternatively, you can compile the code into a native DLL and use it in your C# project via P/Invoke.
If you need to learn P/Invoke, start from here:
http://en.wikipedia.org/wiki/P/Invoke[
^],
http://msdn.microsoft.com/en-us/library/Aa712982[
^].
This CodeProject can also be useful:
Essential P/Invoke[
^].
One alternative to P/Invoke is to use C++/CLI mixed-mode (managed+unmanaged) project. This project could build a DLL, but it can contain some managed wrapper CLI code, so, from the standpoint of your .NET application, you can use it as a regular .NET assembly, that is, reference it. Please see:
http://en.wikipedia.org/wiki/C%2B%2B/CLI[
^],
http://www.ecma-international.org/publications/standards/Ecma-372.htm[
^],
http://msdn.microsoft.com/en-us/library/xey702bw.aspx[
^],
http://msdn.microsoft.com/en-us/library/3bstk3k5[
^].
—SA