feh 一个基于命令行的高速图片查看器，非常实用：
sudo apt-get install feh
When viewing a slideshow, the following keys may be used:
---------------------------------------------------------------------------------------
p Goto previous slide
n Goto next slide
r Reload image (good for webcams)
v Toggle fullscreen
m Show popup menu
w Size window to current image dimensions
h Pause the slideshow (only useful when using
<, > In place editing, rotate 90 degrees right/left
<HOME> Goto first slide
<END> Goto last slide
<ESCAPE> Quit the slideshow
+, = Increase reload delay
-, _ Decrease reload delay
<DELETE> Remove the currently viewed file from the filelist
<CTRL+DELETE> Delete the currently viewed file and remove it from the filelist
x Close current window
q Quit the slideshow
<KEYPAD LEFT> Move the image to the left
<KEYPAD RIGHT> Move the image to the right
<KEYPAD +> Zoom in
<KEYPAD -> Zoom out
<KEYPAD *> Zoom to 100%
<KEYPAD /> Zoom to fit the window
