asciicast2gif

asciicast2gif is a tool for generating GIF animations from
asciicast files
recorded by asciinema.

How it works

Here's how the asciicast->GIF conversion is implemented.

asciicast2gif shell script parses command line arguments and executes Node.js script
(main.js). main.js loads asciicast (either from remote URL or local
filesystem), generates text representation of the screen for each frame
using asciinema-player's
virtual terminal emulator, and sends it to PhantomJS-based renderer script
(renderer.js), which saves PNG screenshots to a temporary directory. Finally,
main.js calls ImageMagick's convert on these PNG images to construct GIF
animation, also piping it to gifsicle to get the final, optimized GIF file.

Note, asciicast2gif doesn't capture screenshots at a fixed frame-rate (e.g. 30 FPS)
like alternative tools. Instead, it generates PNG files for
each screen update, and specifies delay for every image individually (convert -delay <delay-a> 0.png -delay <delay-b> 1.png -delay <delay-c> 2.png ...). When
the screen is idle there're no screenshots generated. This saves disk space and
makes it less work for both convert and gifsicle, while resulting in smaller
GIF file.

Installation

You can install asciicast2gif with npm, use it via Docker image, or build it
from source.

npm package

To install asciicast2gif using npm run:

npm install --global asciicast2gif

Following runtime dependencies need to be also installed:

• ImageMagick
• giflossy (or gifsicle)

Docker image

You can use asciicast2gif through official asciicast2gif Docker
image (automated build on
Docker Hub from this repository).

Pull the image:

docker pull asciinema/asciicast2gif

Use it like this:

docker run --rm -v $PWD:/data asciinema/asciicast2gif [options and arguments...]

You need to mount some local directory at /data so input and output files can
be accessed by the container. Mounting current working directory ($PWD) makes
most sense in majority of cases.

For example, generating GIF from local file, with double speed and Solarized
theme:

docker run --rm -v $PWD:/data asciinema/asciicast2gif -s 2 -t solarized-dark demo.json demo.gif

Running the above, long command can get old very quickly. Creating a shell alias
may be a good idea:

alias asciicast2gif='docker run --rm -v $PWD:/data asciinema/asciicast2gif'

Look at general usage instructions below for all command line
arguments, options etc.

Note: if you want to override gifsicle options (via GIFSICLE_OPTS env var)
when using Docker image you need to pass it via Docker's -e option.

Building from source

Clone the repository:

git clone --recursive https://github.com/asciinema/asciicast2gif.git
cd asciicast2gif

All further commands are assumed to be called from within the checked out
directory.

Install build time dependencies

Both Node.js script (main.js) and page script used by renderer's HTML page
(page/page.js) need to be build from
ClojureScript source code.

You need
Java 8 JDK
and Leiningen.

Install runtime dependencies

Following runtime dependencies need to be installed:

• Node.js
• PhantomJS (optional, see below)
• ImageMagick
• giflossy (or gifsicle)

Install Node.js wrapper for PhantomJS:

npm install

If you don't have PhantomJS available in $PATH at this point it will be
automatically downloaded during
phantomjs-prebuilt
package installation.

Build

To build the scripts run:

lein cljsbuild once main && lein cljsbuild once page 

Usage

asciicast2gif [-t theme] [-s speed] [-S scale] [-w cols] [-h rows] <input-json-path-or-url> <output-gif-path>

Following options are supported:

-t <theme>        color theme, one of: asciinema, tango, solarized-dark, solarized-light, monokai (default: asciinema)
-s <speed>        animation speed (default: 1)
-S <scale>        image scale / pixel density (default: 2)
-w <columns>      clip terminal to specified number of columns (width)
-h <rows>         clip terminal to specified number of rows (height)

Example of generating GIF from asciicast URL, with default options (normal
speed, double pixel density, asciinema theme):

asciicast2gif https://asciinema.org/a/118274.json demo.gif

Example of generating GIF from local asciicast file, with Solarized Dark theme,
double speed (-s 2), single pixel density (-S 1):

asciicast2gif -t solarized-dark -s 2 -S 1 118274.json demo.gif

Setting custom gifsicle options

You can override default options passed to giflossy/gifsicle by setting
GIFSICLE_OPTS environment variable.

Default options when giflossy is installed are:

-k 64 -O2 -Okeep-empty --lossy=80

Default options when gifsicle is installed are:

-k 64 -O2 -Okeep-empty

For example to generate 16 color gif, with level 3 optimizations, set it like this:

GIFSICLE_OPTS="-k 16 -O3"

Debugging

You can set DEBUG=1 environment variable to make the output of the conversion
process more verbose.

Tweaking conversion process

You can pass extra arguments to Node.js script invocation via NODE_OPTS
environment variable.

Limiting node process memory usage

Limit Node's heap size to 512 MB:

NODE_OPTS="--max-old-space-size=512" asciicast2gif ...

Alternatives

There are following alternative tools solving this problem:

• marionebl/svg-term-cli - generates animated SVG from local or asciinema.org hosted asciicast
• tav/asciinema2gif - generates animated GIF from asciinema.org hosted asciicast
• pettarin/asciicast2gif - generates animated GIF from local asciicast
• anishkny/webgif - generates animated GIF from any website: npm i -g webgif && webgif -u https://asciinema.org/a/147023?t=0

License

Copyright © 2017 Marcin Kulik.