Device driver to act as a virtual web camera

I'm looking for writing virtual camera drivers. Does anybody has idea?
Any book that would be helpful or any link.

Adding more details: I have developed a device driver which saves the image to disk and the display uses the device driver to display the image. The performance does not seem good. The fns. that I have used are: //to capture GetDesktopWindow() CreateCompatibleBitmap() Save() //to display WM_MOUSEMOVE giving a call to capture and display every time but the display is not continuous and appears only after window goes out of focus and comes in focus again

Should I use some other technique to record or display images, what will give fruitful results, please help.

Thanks, -mitesh