Maybe the following links are useful to you:

http://www.planet-source-code.com/vb...46320&lngWId=1

http://www.planet-source-code.com/vb...60600&lngWId=1

http://www.planet-source-code.com/vb...28832&lngWId=1

http://www.planet-source-code.com/vb...40839&lngWId=1

http://www.planet-source-code.com/vb...=6630&lngWId=1

In addition, Lavolpe's AlphaImageControl and Olaf's RC5 (Cairo.Drawing) should also be able to implement the functionality you need.