Thursday, December 18, 2014

screencast gifs

Looking to make some GIFs of things that happen on my screen, found byzanz.

$ sudo apt-get install byzanz
byzanz-record -x 1 -y 1 --delay=4 -h 150 -w 700 hello_world.gif


  • -x and -y set origin of capture on screen
  • -h and -w set height and width to capture

I think I need a more clever way to trigger / manage this than just fiddling with CLI options, but it works really well and produces lightweight image files.

I think it would be cool if there were a utility that let me use arrow keys / hjkl / the mouse cursor to visually select a region of the screen. It could return x, y, height, and width, then I’d let byzanz handle the capture.

That can’t be the hardest thing in the world to do.

xdotool seems like kind of a swiss army knife, and has a getmouselocation command. Theoretically, at least, you can have it respond to events, including a mouse click. I can’t quite wrap my head around how this is supposed to work, and my first few attempts fall flat.

GNU xnee might also be promising, but I don’t really get anywhere with it.

Eventually I find an Ask Ubuntu thread on creating screencast gifs, which points to xrectsel, a tool for returning the coordinates and size of a screen region selected with the mouse:

brennen@desiderata 22:06:28 /var/www/workings-book (master) ★  xrectsel "%x %y %w %h"
432 130 718 575%

I wind up with gif_sel:

#!/usr/bin/env bash

# requires:

eval `xrectsel "BYZANZ_X=%x; BYZANZ_Y=%y; BYZANZ_WIDTH=%w; BYZANZ_HEIGHT=%h"`
byzanz-record -x $BYZANZ_X -y $BYZANZ_Y --delay=4 -h $BYZANZ_HEIGHT -w $BYZANZ_WIDTH ~/screenshots/screencast-`date +"%Y-%m-%d-%T"`.gif

I’ll probably wind up with a couple of wrappers for this for different lengths of recording (for starting with dmenu), though it would be nice if I could just have it record until I press some hotkey.