def image_files
      return [] if input.nil?
      valid_extensions = library::VALID_EXTENSIONS
      expansions = Array(valid_extensions).map{|ext| File.join(input, "**", "#{config[:glob]}.#{ext}")}
      files = SpriteFactory.find_files(*expansions)
      files = files.reject{ |file| exclude?(file) }
      files
    end
def image_files
      return [] if input.nil?
      valid_extensions = library::VALID_EXTENSIONS
      expansions = Array(valid_extensions).map{|ext| File.join(input, "**", "#{config[:glob]}.#{ext}")}
      files = SpriteFactory.find_files(*expansions)
      files = files.reject{ |file| exclude?(file) }
      files
    end
----------------------------------------------------------------------------