How to take screenshot (high fps) in Linux (programming)

Question

First of all I want to say that I\'ve been reading a lot about this and I\'ve learnt many ways to do it, but I haven\'t been able to do it in linux.

My project is an amb

Answer 1

Making this work cross platform is likely to be quite a bit of work. If your final target is windows, then why not use the amblone project, which seems to do exactly what you want?

http://amblone.com/guide

At any rate, here is a solution with ffmpeg & graphicsmagick that is pretty fast (on my i7 8GB laptop). ffmpeg captures exactly one screen, reduces it to the smallest square size that it can, pipes the output to graphicsmagick convert, where it is resized to 1x1 pixel and then reports the image rgb values.

#!/bin/bash

mkfifo /tmp/screencap.fifo

while true
    do
        # this version will send the info to a fifo
        # ffmpeg -y -loglevel error -f x11grab -s 1920x1080 -i :0.0 -s 32x32 \
        # -vframes 1 -f image2 -threads 2 - |  gm convert - -resize 1x1 \
        # txt:- > /tmp/screencap.fifo

        # this version will write out the info to the command line
        # and will show you what is going on.
        ffmpeg -y -loglevel error -f x11grab -s 1920x1080 -i :0.0 -s 32x32 \
         -vframes 1 -f image2 -threads 2 - |  gm convert - -resize 1x1 txt:-
    done
exit

This will give you something like the following:

0,0: ( 62, 63, 63) #3E3F3F
0,0: (204,205,203) #CCCDCB
0,0: ( 77, 78, 76) #4D4E4C

The 0,0 is the location of the pixel being read. The numbers in parenthesis are the respective R,G,B values, and the numbers at the end are your typical html-esque hex values. In the case above there is only 1 pixel, but you could (if you wanted to have the cardinal directions as generalized RGB values) simply change the -resize 1x1 part above to -resize 3x3 and you'll get something like:

0,0: ( 62, 63, 65) #3E3F41
1,0: ( 90, 90, 91) #5A5A5B
2,0: (104,105,106) #68696A
0,1: ( 52, 51, 52) #343334
1,1: ( 60, 60, 59) #3C3C3B
2,1: ( 64, 64, 64) #404040
0,2: ( 49, 49, 50) #313132
1,2: ( 60, 60, 60) #3C3C3C
2,2: ( 65, 65, 65) #414141

I'll leave it to you to pass that information to your arduino.

ffmpeg is great, but you'll have to remember to switch out the screen-capture bit (here in my example -f x11grab) with whatever your windows system uses. Here is a SO link that goes into a bit more detail.

If you really insist on making something cross-platform, then I would recommend diving into openCV with python bindings and using the framebuffer device as a video input, scaling the result down to 1x1 pixel and using the resulting color average to drive your pwm through some type of UDP broadcast.