Transform rectangular image into trapezoid

In .NET 开发者_开发百科how can I transform an image into a trapezoid. The Matrix class supports rotation, shear, etc, but I can't see a trapezoidal transformation.

I'm using the usual System.Drawing.* API, but I'm flexible to other .NET solutions.

I just found this: http://www.vcskicks.com/image-distortion.html

It works great

You need a projective transformation which can be represented by a 3x3 matrix. I've explained how to obtain this transformation matrix in great detail in this SO solution.