What is the most efficent way to screen capture? Screen capturing using DirectX?

I've known about screen capture using Device Contexts and GDI, since windows XP. Is there a better way (i.e. DirectX?) now that the desktop is mostly Direct3D.

How can I screen capture using DirectX?

I want to know the most efficent way to user-mode screen capture. For a tech support program that needs frequent screen scrapes.

UPDATE: I don't want to resort to usin开发者_如何学Cg kernel mode drivers.

I am unsure this will actually be faster than the algorithms you have in mind, but one way to do it would be to copy your buffer out using GetRenderTargetData.

GetRenderTargetData

Based upon vcsjones answer (above). See CodeProject http://www.codeproject.com/KB/dialog/screencap.aspx#And%20The%20DirectX%20way%20of%20doing%20it%20

An alternative method is using Spazzarama's application, which uses DirectX (based on SlimDx) and Easyhook to inject your capture dll into a running application's DirextX pipeline.