stitches a collection of images vertically, and upscales/downscales to a specific width

stitch.rb

#!/usr/bin/env ruby

# Licensed under MIT. (c) 2022 Julian A Avar Campopiano

# Requires ruby3.0.0 and imagemagick
# Usage:
#     stitch.rb [options] -i=[glob] -o=[glob]
# Example:
#     stitch.rb -w=min -i=*.jpg
#     stitch.rb -w=259.3 -i=photo_{a,b}.png -o=out_file.png

def get_input()
	input = ARGV.map do |arg|
		width = arg.match(/^$|^(--width|-w)=(min|max|avg|\d+(\.\d+)?)$/)
		input_img = arg.match(/^$|^(--input|-i)=(\S+)$/)
		output_img = arg.match(/^$|^(--output|-o)=(\S+)$/)
		
		if width != nil
			[:width, width[2]]
		elsif input_img != nil
			[:input, input_img[2]]
		elsif output_img != nil
			[:output, output_img[2]]
		else
			nil
		end
	end.to_h
	
	input[:width]  = "min"     unless input.has_key?(:width)
	input[:input]  = "*.*"     unless input.has_key?(:input)
	input[:output] = "out.png" unless input.has_key?(:output)
	
	return input
end

def main()
	input = get_input()
	
	puts input.to_a.map { |pair| "#{pair[0].to_s}=#{pair[1].to_s}"}.join("\n")
	
	all_images_width = `magick identify -format '%[fx:w] ' #{input[:input]}`.split(" ").map { |w| w.to_i }
	
	width = case input[:width]
		in "min" then all_images_width.min
		in "max" then all_images_width.max
		in "avg" then all_images_width.then{ |a| a.sum.to_f / a.size }.floor
		in w then w.to_f.floor
	end
	
	`magick #{input[:input]} -resize #{width} -append #{input[:output]}`
end

main() if $PROGRAM_NAME == __FILE__