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To take a static screenshot of a selected part of my screen, I often use scrot with -s shot.png. This is great for adding illustrations to StackExchange posts. I even found this script to automatically upload such a screenshot to Imgur.com and put a link in my X clipboard!

Let's turn this up to twelve: How do I similarly create a GIF screencast?

There are programs like recordmydesktop, byzanz & co as discussed on Ask Ubuntu that aim to be "user friendly", but in my experience are buggy, inefficient, mostly unscriptable and unsuited for little one-off things like this.

I just want to select an area and record a GIF, with a console command I can understand, not some arcane unscriptable GUI monstrosity.

How can I do this?

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Related: How to create animated GIF images of a screencast? from Ask Ubuntu. –  Cristian Ciupitu Oct 20 at 12:36

2 Answers 2

up vote 23 down vote accepted

OK then

ffcast -s ffmpeg -r 20 -vcodec huffyuv out.avi
convert -layers Optimize -set delay 10 out.avi out.gif

GIF vimcast!

I started ffcast, did some vim, quit ffcast, then converted the .avi to .gif.

I ran the recording commands in another terminal. More polished script for your $PATH at the end of this answer.

What happened?

Capturing

FFcast helps the user interactively select a screen region and hands over the geometry to an external command, such as FFmpeg, for screen recording.

ffcast is the glorious product of some hacking at the Arch Linux community (mainly lolilolicon). You can find it on github (or in the AUR for Archers). Its dependency list is just bash, ffmpeg, libx11, xorg-dpyinfo and xorg-xwininfo.

Internally, it works by invoking xrectsel from libx11 (the same standard function scrot uses) and letting the user select a screen region. It then substitutes the correct dimensions for %x, %y, %w, %h and %d in the given command. There's a preset for ffmpeg, which automatically inserts the correct selection area flags for it to record video.

You can also append ffmpeg flags right after the command. I set -r 15 to capture at 15 frames per second and -vcodec huffyuv for lossless recording. (Play with these if you want a different size/quality tradeoff.)

GIFfing

ImageMagick can read .avi videos and has some GIF optimisation tricks that drastically reduce file size while preserving quality: The -layers Optimize to convert invokes the general-purpose optimiser. The ImageMagick manual has a page on advanced optimisations too.

Final script

This is what I have in my $PATH to initially record into a temporary file.

#!/bin/bash
TMP_AVI=$(mktemp /tmp/outXXXXXXXXXX.avi)
ffcast -s ffmpeg -y -r 20 -vcodec huffyuv $TMP_AVI \
&& convert -set delay 10 -layers Optimize $TMP_AVI out.gif

Wheeeeee!

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This is really cool. Thanks for sharing. –  WhiteHotLoveTiger Feb 5 at 18:35
1  
I've created a version who doesn't require bash, but who works on any POSIX compliant shell github.com/chilicuil/ffcast –  chilicuil Mar 22 at 4:31
2  
Looks like the command line syntax of ffcast has changed: github.com/lolilolicon/FFcast/issues/8 –  Jack O'Connor Sep 30 at 20:25
1  
The simplest way to do it is now ffcast -s rec [filename], though that doesn't give the exact settings you're using in your example. Unfortunately, to give exact settings, you now have to give the entire ffmpeg command. Your call about the best way to update this answer :) –  Jack O'Connor Oct 1 at 1:47
4  
Based on the comments on GH, ffcast -s % ffmpeg -f x11grab -show_region 1 -framerate 20 -video_size %s -i %D+%c -codec:v huffyuv -vf crop="iw-mod(iw\\,2):ih-mod(ih\\,2)" $TMP_AVI seems to do the trick. –  BenC Oct 1 at 10:35

For me, the answer was to use ffcast with ffmpeg like so:

ffcast -w % ffmpeg -f x11grab -show_region 1 -framerate 20 -video_size %s -i %D+%c -codec:v huffyuv -vf crop="iw-mod(iw\\,2):ih-mod(ih\\,2)" out.avi

I then used ffmpeg to do the conversion from avi to gif - it's very fast and it keeps the framerate intact:

ffmpeg -i out.avi -pix_fmt rgb24 out.gif

Lastly I used convert in the same way as @anko's answer to optimise the gif, but I set a limit on resource usage to stop convert exiting with a killed message, and I removed the delay as ffmpeg has already handled that:

convert -limit memory 1 -limit map 1 -layers Optimize out.gif out_optimised.gif
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