Use imageconvert to make icons.

gistfile1.txt

def system(cmd)
	puts cmd
	Kernel.system(cmd)
end

def convert(filename, size)
	ext = File.extname(filename)
	base = File.basename(filename, ext)
	dir = File.dirname(filename)

	# download imageconvert here: https://github.com/slembcke/ImageConvert
	system "./imageconvert #{size} #{filename} #{File.join(dir, "Icon-" + size.to_s + ".png")}"
end

filename = ARGV[0]
# You could glob it too: (Dir.glob(ARGV[0])).each do|filename|
	convert(filename, 29)
	convert(filename, 40)
	convert(filename, 50)
	convert(filename, 58)
	convert(filename, 57)
	convert(filename, 72)
	convert(filename, 76)
	convert(filename, 80)
	convert(filename, 100)
	convert(filename, 114)
	convert(filename, 120)
	convert(filename, 144)
	convert(filename, 152)
	convert(filename, 180)
#end