说明：  将一个矩阵图在指定的屏幕全屏显示，当你想退出时，利用ALT-TAB键切换出来便可关闭全屏窗口
(FULLSCREEN(C,N) displays matlab image matrix C on display number N (which ranges from 1 to number of screens). Image matrix C must be the exact resolution of the output screen since no scaling in implemented. If fullscreen is activated on the same display as the MATLAB window, use ALT-TAB to switch back.)