3.3.5.2.4 MILCMD_TARGET_CAPTUREBITS
This message is sent by the server to request a copy of render target contents. The client must respond by sending a MILMSG_CAPTUREBITSREPLY notification containing a copy of the render target pixels. This message MUST be sent on the backchannel corresponding to the channel on which the MILCMD_TARGET_CAPTUREBITS message was received. The MILCMD_TARGET_CAPTUREBITS fields are used as follows:
x, y: Specify the offsets in render target coordinates from which pixels are to be read.
width, height: The width and height of capture area in render target coordinates.
dxgiFormat: The DXGI_FORMAT pixel format for the returned render target area.