在gnome3下compiz已经无法使用，以前使用的快捷键已经无法使用，这里可以同样设置，达到视觉效果和实用效果的双重效果
1 设置已有快捷键
System-tools>>System Settings
2 设置截屏快捷键
补充一下：抓图Take Screenshot的参数
–window Takes a screenshot of the window that has focus.
–delay=seconds Takes a screenshot after the specified number of seconds,
and displays the Save Screenshot dialog.
Use the Save Screenshot dialog to save
the screenshot.
–include-border
Takes a screenshot including the border of the window.
–remove-border
Takes a screenshot without the border of the window.
–border-effect=shadow
Takes a screenshot and adds a shadow bevel effect around it.
–border-effect=border
Takes a screenshot and adds a border effect around it.
–interactive
Opens a window that lets you set options before taking the screenshot.
–help
Displays the options for the command.
比如我们要实现
–window 抓取当前激活窗口
–interactive 先显示抓图软件界面，再抓图。
–delay=2 延时2秒钟后抓取
命令：gnome-screenshot –window –interactive –delay=2
该命令可以在终端窗口中运行。大家可以根据需要自行修改。