How to make transparent GIFs more easily sharable by adding a checkerboard background

I’m currently taking part in the "#hARToween" daily art challenge, as I want to work on my pixelart skills and drawing a 128x128px pixel drawing each day¹ for a month seemed like a good idea. You can follow my posts in this thread.

I’m using Aseprite, and recently came across the “record for aseprite” script for it that allows taking regular snapshots of what I’m currently drawing so a timelapse can be created from that. And that works nicely, but I had to realize that the timelapse would come with transparency until I came to the background during my drawing, which looked really weird when sharing the resulting GIF.

So I looked into adding the usual transparency checkerboard background to the GIF with a quick script, and of course, ImageMagick once more to the rescue. Alas, the resulting GIF was quite large and ImageMagick’s optimization options caused glitches in the GIF. So I looked for another option to optimize the GIF and came across gifsicle.

The result is this bash script which will take a GIF and an optional background image to set, add the background (or a freshly generated checkerboard pattern of the right size) to the GIF, then compress the GIF:

#!/bin/bash

GIF=$1
BG=$2

BASE=$(basename "${GIF%.*}")
OUTPUT="$BASE.bg.gif"

if [ -f "$BG" ]; then
    echo "Adding background image $BG to all frames of $GIF..."
    magick "$GIF" -coalesce null: "$BG" -compose dstOver -layers composite "$OUTPUT"
else
    size=$(gifsicle --sinfo "$GIF" | grep "logical screen" | xargs echo -n | cut -d" " -f 3)

    echo "Generating a $size checkerboard pattern and adding it as background to all frames of $GIF..."
    magick "$GIF" -coalesce null: \( -size $size tile:pattern:checkerboard \) -compose dstOver -layers composite "$OUTPUT"
fi

echo "Optimizing $OUTPUT..."
gifsicle --batch -O3 --lossy=35 "$OUTPUT"

echo "...done!"

Example call:

$ gif_bg 14.gif 
Generating a 256x256 checkerboard pattern and adding it as background to all frames of 14.gif...
Optimizing 14.bg.gif...
...done!

I’m quite happy with the result:

Gina Häußge @foosel@chaos.social

Now also with a creation timelapse (after I finally managed to get a proper workflow going for that)

October 14, 2024, 14:43 (UTC)