基于Qt4下的截屏并保存在QPixmap，这个QWidget上进行跟QQ截图有点象完成后点鼠标右键就有ContextMenu弹出Esc为退出，空格键保存图像(当然也可以右键菜单保存)-Qt4-based cut-off under the screen and save it in QPixmap, this QWidget with QQ on the screenshot a bit like the right mouse button after the completion point