TileSheet class for Gosu in Ruby

tilesheet.rb

# tilesheet.rb
#
# This is for loading tile sheets that either have padding between the tiles,
# do not take up the whole of the image, or both.  The normal Gosu method for
# loading from tiles doesn't work if there is padding or the tiles themselves
# are not wall-to-wall on the sheet.  This can load such a sheet, though you
# will need to know how many tiles there are both wide and tall, as there's no
# way to guess on such a sheet.  You'll also need to make sure the sheet is a
# power-of-two in size.  You can do this by adjusting the sheet to 512x512 or
# 1024x1024, just add empty space if needed.
#
# This also relies on experimental Gosu::Image.subimage, which may vanish in a
# future version of Gosu.  Don't get too attached.
class TileSheet
  def initialize(source, tiles_wide, tiles_tall, tile_width, tile_height, tile_padding = 0)
    @tile_sheet = Gosu::Image.new(source, { :tileable => true, :retro => true })
    @tiles_wide = tiles_wide
    @tiles_tall = tiles_tall
    @tile_width = tile_width
    @tile_height = tile_height

    # Padding is assumed to be between tiles, but not between the tiles and the
    # outside borders.  As in 0,0 is the top left pixel of the first tile, not
    # padding.  If you have a sheet with padding in the borders as well these
    # aren't the droids you're looking for, sorry.
    @tile_padding = tile_padding

    # An array of subimages
    @tiles = []

    # Generate all of the sub-images
    @tiles_tall.times do |y|
      @tiles_wide.times do |x|
        @tiles.push(@tile_sheet.subimage((x * @tile_width) + (x * @tile_padding), (y * @tile_height) + (y * @tile_padding), @tile_width, @tile_height))
      end
    end
  end

  # Lets you get the subimages using array syntax, so that a TileSheet can be a
  # drop-in replacement for an array of Gosu::Image
  def [](tile)
    @tiles[tile]
  end

  # In case you just want the array itself instead.  That's cool too, I'm easy
  # like Sunday mornin'.
  def to_a
    @tiles
  end
end