HornetsEye allows you to capture frames from videos by using MPlayer

#!/usr/bin/env ruby
require 'hornetseye'
raise "Syntax: inputcolour.rb <video file> <output image> <skip>" if ARGV.size != 3
input = Hornetseye::MPlayerInput.new( ARGV[0] )
ARGV[2].to_i.times { input.read }
img = input.read_ubytergb
img.save_ubytergb ARGV[1]