///|
/// Convert grayscale pixels to RGBA for display
pub fn grayscale_to_rgba(
  pixels : FixedArray[Byte],
  width : Int,
  height : Int,
) -> FixedArray[Byte] {
  let rgba_size = width * height * 4
  let rgba = FixedArray::make(rgba_size, b"\x00"[0])

  for y in 0..