Is there some high level method I can use
Visual C# General
You'd probably have to use edge detection to find a bounding rectangle for the area you want to crop. It's a rather complex task. http://www.umiacs.umd.edu/~hankyu/shape_html/ is a paper on using edge detection to find shapes in images.
http://www.codeproject.com/cs/media/edge_detection.asp df=100&forumid=3567&exp=0&select=1227293 might be useful.