High Quality Image Resizing in ASP.net

I've been searching everywhere for a good way to resize images in ASP.net. So far, I have used every tip I could find.

- Set the System.Drawing.Graphics object property SmoothingMode to HighQuality

- Set the System.Drawing.Graphics object property CompositingQuality to HighQuality

- Set the System.Drawing.Graphics object property InterpolationMode to High

Unfortunately, I still see a good deal of artifacts created from the shrinking. I am seeking ideas and help. I am going from roughly 20Megapixel down to about 640X480. I am willing to try just about anything.

Thanks in advance to anyone who can help!