5c0a986e ​

let p1: (Int, Int)
let p2: (Int, Int)

let input = fill 10 (fill 10 black)
  |> rect ((p1.1, p1.2, p1.1 + 1, p1.2 + 1), blue)
  |> rect ((p2.1 - 1, p2.2 - 1, p2.1, p2.2), red)

let output = fill 10 (fill 10 black)
  |> rect ((p1.1, p1.2, p1.1 + 1, p1.2 + 1), blue)
  |> rect ((p2.1 - 1, p2.2 - 1, p2.1, p2.2), red)
  |> rep1 (-1, -1) [(p1.1, p1.2, blue)]
  |> rep1 (1, 1) [(p2.1, p2.2, red)]