How to copy the pixel data from a texture into a bitmap (direct3d)?

Question

I have rendered the scene into a texture, and then I want to save it into a bitmap, but after lock the texture, I found there is no pixel data in the lock area. The texture can be displayed correctly on the screen. I am not sure why? 1> the format is incorrect? A8R8G8B8 has been used. 2> have I missed some important steps before get the pixel data?

Answer 1

Doing readback from Direct3D textures and surfaces