Shell script to create nice-looking animated Discord stickers. Supports processing several files in parallel.

discticker.sh

#!/bin/sh -e

# Shell script to convert videos to APNG images suitable for use as Discord
# stickers. Tools used:
# - ffmpeg
# - pngquant
# - apngasm

while getopts r:f:p:m:h option; do
	case $option in
		r) # Resolution
			RESOLUTION="$OPTARG";;
		f) # FPS
			FPS="$OPTARG";;
		p) # Palette size
			PALETTE_SIZE="$OPTARG";;
		m) # Duration multiplier (useful for squeezing a bit more content in the 5 second limit)
			DURATION_MULTIPLIER="$OPTARG";;
		h|*) # Help
			echo "Usage: $0 [-r WxH] [-f FPS] [-p PALETTE_SIZE] [-m DURATION_MULTIPLIER]"
			exit 1;;
	esac
done

readonly RESOLUTION="${RESOLUTION:-132x132}"
readonly FPS="${FPS:-16}"
readonly PALETTE_SIZE="${PALETTE_SIZE:-32}"
readonly DURATION_MULTIPLIER="${DURATION_MULTIPLIER:-1}"

WORK_DIRECTORY=$(mktemp -d -t discticker.XXX)
readonly WORK_DIRECTORY

trap 'rm -rf "$WORK_DIRECTORY"' EXIT INT TERM

shift $((OPTIND - 1))

for video in "$@"; do
	{
		video_basename="${video##*/}"
		result_file="${video_basename%.*}.png"

		mkdir "$WORK_DIRECTORY/$video_basename"

		ffmpeg -hide_banner -i "$video" \
			-filter:v "setpts=$DURATION_MULTIPLIER*PTS,fps=$FPS,trim=duration=4.95" \
			-s "$RESOLUTION" \
			"$WORK_DIRECTORY/$video_basename/frame%03d.png"

		pngquant --speed 1 --ext .png --force "$PALETTE_SIZE" -- "$WORK_DIRECTORY/$video_basename"/frame*.png
		apngasm "$result_file" "$WORK_DIRECTORY/$video_basename"/frame*.png 1 "$FPS" -z2

		result_size=$(stat -c%s "$result_file")

		if [ "$result_size" -ge $((512 * 1024)) ]; then
			echo "! $result_file exceeds the 512 KiB Discord size limit. Aborting conversion"
			rm "$result_file"
		else
			echo "> Sticker stored at $result_file ($((result_size / 1024)) KiB)"
		fi
	} &
done

wait