T Colour = Vec3b

V black = Colour(0, 0, 0)
V white = Colour(255, 255, 255)

T Bitmap
   Int width, height
   Colour background
   [[Colour]] map

   F (width = 40, height = 40, background = white)
      assert(width > 0 & height > 0)
      .width = width
      .height = height
      .background = background
      .map = [[background] * width] * height

   F fillrect(x, y, width, height, colour = black)
      assert(x >= 0 & y >= 0 & width > 0 & height > 0)
      L(h) 0 .< height
         L(w) 0 .< width
            .map[y + h][x + w] = colour

   F chardisplay()
      V txt = .map.map(row -> row.map(bit -> (I bit == @@.background {‘ ’} E ‘@’)).join(‘’))
      txt = txt.map(row -> ‘|’row‘|’)
      txt.insert(0, ‘+’(‘-’ * .width)‘+’)
      txt.append(‘+’(‘-’ * .width)‘+’)
      print(reversed(txt).join("\n"))

   F set(x, y, colour = black)
      .map[y][x] = colour

   F get(x, y)
      R .map[y][x]

V bitmap = Bitmap(20, 10)
bitmap.fillrect(4, 5, 6, 3)
assert(bitmap.get(5, 5) == black)
assert(bitmap.get(0, 1) == white)
bitmap.set(0, 1, black)
assert(bitmap.get(0, 1) == black)
bitmap.chardisplay()