Generated GIFs are very inefficient in space

[ahmetb]

Take a look at this GIF, it goes on FOR MINUTES and it's only 32 kb:

https://github.com/tianon/gosleep/blob/master/example.gif

I'm curious why we can't we have this minimality with asciicast2gif? My 30 second recording is 964 kilobytes.

Is there a way to minimalize this? I don't care about antialiasing and all those fancy stuff making the image larger.

[publicarray]

There are many factors to the file size. The example.gif is only 497×290 pixels, uses few colours, is short (~28 seconds) and has a low area of change between frames (easier to compress).

asciicast2gif already uses gifsicle to compress the output gif, but there are more options from gifsicle that you can try.

BTW the -S option in asciicast2gif is for up-scaling, you probably want to set it to 1.

[publicarray]

You can also ask @tianon how the gif was generated.

[tianon]

Was a pretty standard byzanz (https://github.com/GNOME/byzanz) recording -- nothing very custom there.

[publicarray]

Thanks for chiming in. Cool project for GNOME users.

[tianon]

Heh, I don't use GNOME -- I actually ran it inside a Docker container, and had a small wrapper script to grab the proper X, Y, width, and height for capturing the window I was interested in. It doesn't need more than the X11 socket in order to work. 👍

[ku1ik]

@ahmetb can you give us a link to your recording which ends up being 964kb gif? We can play with various arguments for asciicast2gif and for gifsicle.

[ahmetb]

https://asciinema.org/a/dD9UhCIaPw13znirhmGUnNJtd

[publicarray]

I've played a little with ImageMagick and gifsicle

Command	Size (KB)	Savings (KB)
asciicast2gif 'https://asciinema.org/a/dD9UhCIaPw13znirhmGUnNJtd.cast?dl=true' out.gif	941	0
asciicast2gif 'https://asciinema.org/a/dD9UhCIaPw13znirhmGUnNJtd.cast?dl=true' out.gif -S 1 *	348	593
gifsicle --optimize -O3 --colors 16 -o out-16.gif out.gif	336	593+12
convert out.gif -coalesce -layers RemoveDups -layers RemoveZero -layers OptimizeFrame out-dedupe.gif	321	593+27
convert out.gif -coalesce -layers RemoveDups -layers RemoveZero -layers OptimizeFrame - | gifsicle --optimize -O3 -o out-dedupe-gifsicle.gif	259	593+89
convert out.gif -coalesce -layers RemoveDups -layers RemoveZero -layers OptimizeFrame - | gifsicle --optimize -O3 --colors 16 -o out-dedupe-16.gif	253	593+95
convert out.gif -coalesce -layers RemoveDups -layers RemoveZero -layers OptimizeFrame - | gifsicle --optimize -O3 --colors 6 --use-colormap=gray -o out-dedupe-bw.gif	175	593+173

* The scaled=1 gif is used as an input for all remaining commands

[ku1ik]

@publicarray awesome! That's very helpful.

Another things to try:

• check out giflossy instead of gifsicle (see Consider giflossy as alternative to gifsicle #1)
• use gifsicle to assemble frames instead of ImageMagick (see Use gifsicle to assemble frames instead of ImageMagick? #3)

I'm thinking that maybe asciicast2gif could have a concept of "presets", probably 3 (low, normal, high) would be enough to cover everyone's needs. But before presets, I'd like to try the above.

[ahmetb]

It'd be really cool to script these into a separate tool, or bundle in the asciicast2gif tool?

[ku1ik]

I've implemented some optimizations:

• the biggest impact on filesize was too high frame-rate - it's capped at 15fps now
• added support for giflossy (if giflossy is installed instead of gifsicle the options passed to gifsicle command are extended with -lossy=80)

I've pushed new version to npm, and there's new image on Docker hub (docker pull asciinema/asciicast2gif if you previously pulled it).

You can set GIFSICLE_OPTS env var to override the options passed to gifsicle, which is great for experimenting with different color/optimization/lossyiness combinations.

[ku1ik]

I've generated gif from the asciicast linked by @ahmetb using latest (today's) version, with this command:

asciicast2gif -S 1 https://asciinema.org/a/dD9UhCIaPw13znirhmGUnNJtd.cast ahmetb.gif

Or Docker version:

docker run --rm -v $PWD:/data asciinema/asciicast2gif -S 1 https://asciinema.org/a/dD9UhCIaPw13znirhmGUnNJtd.cast ahmetb.gif

The resulting gif is 213kb, which is a good improvement over initial 964kb.

[ahmetb]

Thanks a bunch, that's a pretty good improvement!