Convert an Animated GIF to an image table

to-table.sh

#!/usr/bin/env bash

display_usage() {
	echo "This script must be passed an Animated GIF."
	echo
	echo "Usage: $0 image-table-32-32.gif [width-in-cells]"
}
# if less than two arguments supplied, display usage
if [  $# -lt 1 ]
then
	display_usage
	exit 1
fi
# check whether user has supplied -h or --help, display usage
if [[ ( $# == "--help") ||  $# == "-h" ]]
then
	display_usage
	exit 0
fi

# -----

# input file details
fullname=$(basename -- "$1")
filename="${fullname%.*}"

# extract cell size from filename
regex_anim=".*\-table\-([0-9]+)\-([0-9]+)\.gif"
if [[ ${fullname} =~ ${regex_anim} ]]
then
	W="${BASH_REMATCH[1]}"
	H="${BASH_REMATCH[2]}"
else
	display_usage
	exit 1
fi

# check argument 2 is a number
regex_number='^[0-9]+$'
if ! [[ ${2} =~ ${regex_number} ]]
then
	echo "error: [width-in-cells] needs to be a number" >&2
	exit 2
fi

# if argument 2 is passed set tile parameter
if [[ $2 ]]
then
	tile="-tile ${2}x"
else
	tile=""
fi

# convert to image table PNG
magick montage "$1" $tile -geometry "1x1+0+0<" -alpha On -background transparent "${filename}.png"

# output specifications
magick identify -format "${filename}.png: %w x %h pixels\n" "${filename}.png"