fbgrab - takes screenshots using the framebuffer device

   fbgrab [options] filename

   fbgrab  reads  the  framebuffer device (/dev/fb*) or a dump thereof and
   saves a PNG image file. You can use it for  making  screenshots  of  of
   virtually  any  application, from traditional test applications to your
   X-windows desktop, as well as framebuffer applications.

   -?     print usage information.

   -a     ignore the alpha channel, to support pixel formats like BGR32.

   -b bitdepth
          the number of bits per pixel used, optional  when  reading  from
          device.

   -c console
          specifies which console (or virtual terminal - like other people
          call this feature) to grab. Sometimes this  changing  is  faster
          then  the  framebuffer  is  refreshed  (especially when grabbing
          framebuffer apps). If so, you should use  -C  console  ...  This
          waits some time before grabbing. You can't use -s in this case.

   -d device
          specifies  which  framebuffer device you want to read. If you do
          not use this option, it takes the  value  from  the  FRAMEBUFFER
          environment  variable. If no FRAMEBUFFER environment variable is
          given or if its value is NULL, then DEFAULT_FB  is  taken.  (see
          source code), which usually is /dev/fb0.

   -f filename
          Read from from file instead of device, requires that -w (width),
          -h (height) and -b (bitdepth) are specified.

   -h height
          the height of the frambeuffer in pixels, optional  when  reading
          from device.

   -i     turns off interlacing. If you do not want ADAM7 interlacing, you
          should use the -i option.

   -l line length, a.k.a. stride.
          the length  in  pixels  between  the  start  of  each row in the
          framebuffer, which might be larger or equal  to  width. Optional
          when reading from device.

   -s seconds
          specifies how many seconds to wait before grabbing. fbshot  does
          not  lock console switching, so you can switch it while waiting,
          if you cannot use -c requires normally that  fbgrab  is  run  as
          root.

   -v verbose
          be verbose

   -w width
          the  width  of  the frambeuffer in pixels, optional when reading
          from device.

   -z     set png compression level 0 (fast) to 9 (best).

   * Low-end bit depths, eg 1, 2, 4 & 8 bits.

   * Companion program fbput that would display a  picture  in  the  fram‐
   buffer.

   * Better utilization of the PNG-lib, all formats are first converted to
   32 bitdepth and then stored as PNG - hardly the right approach.

   fbgrab fb.png

   will take a framebuffer snapshot, or if you don't have fbgrab  at  your
   machine, you can do

   cp /dev/fb0 framebuffer.dump

   and then

   fbgrab -w 1024 -h 768 -b 16 -f framebuffer.dump fb.png

   to convert it to a picture.

Fix pixel format report

When fbgrab tells about the framebuffer pixel format, blue and green
are accidentally swapped in 'length' and 'msb_right' columns. Let's
order everything as RGB.

Thanks to Timo Ketola.