LinuxQuestions.org - How to take a screenshot with /dev/fb0

- Slackware (https://www.linuxquestions.org/questions/slackware-14/)

- - How to take a screenshot with /dev/fb0 (https://www.linuxquestions.org/questions/slackware-14/how-to-take-a-screenshot-with-dev-fb0-918705/)

How to take a screenshot with /dev/fb0

I would like to take a framebuffer screenshot
from the command line and have been trying to
use

Code:

cp /dev/fb0 file

I have been switching to tty2 with Alt-F2 to do this
but keep winding up with a screenshot of whatever is
on the tty2 screen. How do I specify tty1's screen?

I am aware that I could use /dev/vcs1 to do this
but that only gives me a text representation instead
of a raw screen dump that I can then later convert
to PNG.

perhaps you could do...

*CTRL-ALT-F2*
sleep 2 && cp /dev/fb0 file
*CTRL-ALT-F1*

why not use fbdump as you can see it should do what you want

Code:

keithhedger@SlackHolly:~-> fbdump --help

fbdump 0.4.2



(c) Richard Drummond 2001-2007



Dumps the contents of the framebuffer to stdout as a PPM file.

Usage:

  -fb <string>   Path to the framebuffer device to dump is <string>

  -vt <n>        Bring virtual terminal no. <n> to the foreground before dumping

  -delay <n>     Wait <n> seconds before dumping

  --help         Show this help

I would have bet a lot of money that someone would recommend delaying the snapshot long
enough to revert to the Alt-F1 screen so /dev/fb0 would refer to the proper screen. That
does give me a nice 3MB or so raw file which can be converted to .png as follows:

Code:

iraw2png 1024 768 < screenshot.raw > screenshot.png

I tried fbdump --help but apparently I don't have that on my Slack 13.37 64 bit system.

I was under the impression that there were several /dev/fb's since multi-screen comfigurations
are possible but in /dev there is only one; fb0. Apparently multi-screen is only available
in xorg with a xorg.conf file altered to indicate multiple screens. Kind of makes me wonder
just what difference there is between /dev/vcs1... and /dev/fb0. Only /dev/fb0 will get
you a raw screen dump whereas /dev/vcs... will only get a text representation of the
screen and no graphics.

Sorry fbdump is available at slackbuilds.org