H*g
2 楼
video overlay，估计相当于以前dos里的直接写屏。
H*g
3 楼
http://en.wikipedia.org/wiki/Hardware_overlay
As a consequence of hardware overlay use, a screenshot program (for example,
the one automatically built into Windows that activates when a user presses
the PrtSc key) often does not capture the content appearing in the hardware
overlay window. Rather, a blank region containing only the special mask
color is captured. This is because the screen capture routine doesn't
consider the special video memory regions dedicated to overlays – it simply
captures the shared main screen as rendered by the software's graphical
subsystem
As a consequence of hardware overlay use, a screenshot program (for example,
the one automatically built into Windows that activates when a user presses
the PrtSc key) often does not capture the content appearing in the hardware
overlay window. Rather, a blank region containing only the special mask
color is captured. This is because the screen capture routine doesn't
consider the special video memory regions dedicated to overlays – it simply
captures the shared main screen as rendered by the software's graphical
subsystem
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