Ambrevar / Emacs Gif Screencast

#+TITLE: Emacs GIF Screencast

One-frame-per-action GIF recording for optimal quality/size ratio.

See [[https://github.com/emacs-helm/helm-system-packages][Helm System Packages]] for examples.

• Rationale

Most Emacs screencasts are done by first recording a video, then converting it to a [[https://en.wikipedia.org/wiki/GIF][GIF]]. It seems like a waste of resources considering the little animation Emacs features.

Most of the time, one user action equals one visual change. By exploiting this fact, this package tailors GIF-screencasting for Emacs and captures one frame per user action. It's much more efficient than capturing frames even at a frequency as low as 10 per second. You could roughly expect 3 to 10 times smaller files compared to videos of the same quality. (Benchmarks are welcome.)

Conversely, should your Emacs demo feature self-animated content (such as output scrolling in Eshell), no frame will be captured. A workaround consists in hammering some no-op key such as forward-char or end-of-line.

Another neat perk of action-based captures is that it produces /editable/ GIF files: programs such as [[https://www.lcdf.org/gifsicle/][Gifsicle]] or [[https://www.gimp.org/][The GIMP]] can be used to edit the delays or rearrange frames.

This is particularly useful to fix mistakes in "post-processing", without having to record the demo all over again.

• Features, pros and cons

• Recordings can be paused and resumed.

• Resulting GIF files are editable, which allows for post-processing / fixing.

• Quality is top notch.

• File-size is optimal.

• The result might feel a tad jittery sometimes.

• It won't render self-animated content such as auto-scrolling, this is workable however.

• It should be much lighter on memory and CPU than video recording.

• Implementation

Upon start, it adds gid-screencast-capture to pre-command-hook which makes every command (including those called by key presses) take a screenshot. On each screenshot, it records the timestamp.

If paused then resumed, the timestamps are offset by the length of the pause.

When stopped, it compiles the screenshots together into a GIF file using the timestamps to set the appropriate delays for each frame.

• Setup

You'll need a screenshot program and a GIF converter. Defaults are:

• gif-screencast-program: [[http://scrot.sourcearchive.com/][scrot]]
• gif-screencast-convert-program: [[https://imagemagick.org/script/convert.php][convert]] (from the ImageMagick suite)
• Optional: gif-screencast-optimize-program: [[https://www.lcdf.org/gifsicle/][Gifsicle]]

You can pass arguments to the screenshot program via git-screencast-args to command it to capture only part of the screen, e.g. you can restrict the capture to the Emacs frame with =scrot='s argument =--focused=

You might want to set some bindings for convenience.

#+BEGIN_SRC emacs-lisp (with-eval-after-load 'gif-screencast (define-key gif-screencast-mode-map (kbd "") 'gif-screencast-toggle-pause) (define-key gif-screencast-mode-map (kbd "") 'gif-screencast-stop)) #+END_SRC

Start recording with gif-screencast!

** macOS

macOS requires some additional settings:

#+BEGIN_SRC emacs-lisp (with-eval-after-load 'gif-screencast (setq gif-screencast-args '("-x")) ;; To shut up the shutter sound of screencapture' (seegif-screencast-command'). (setq gif-screencast-cropping-program "mogrify") ;; Optional: Used to crop the capture to the Emacs frame. (setq gif-screencast-capture-format "ppm") ;; Optional: Required to crop captured images. #+END_SRC

[[https://imagemagick.org/script/mogrify.php][mogrify]] is part of the ImageMagick suite.

** Display pressed keys while recording

The [[https://github.com/tarsius/keycast][KeyCast]] package is useful to dispay the pressed keys in the modeline while recording.