how to copy bits from minimized window's HDC?

i would like to copy entire client window size of some window to my HDC, but when the window is minimized the source of all color bit开发者_如何学运维s is always empty RGB(0,0,0); How to do this without activating the window?

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You can use this function:

BOOL PrintWindow(
    HWND hwnd,
    HDC hdcBlt,
    UINT nFlags);

http://msdn.microsoft.com/en-us/library/dd162869%28v=vs.85%29.aspx