Useful sprite draw function for PICO-8 (and maybe Lua in general)

outline_sprite.p8.lua

--
-- draws a sprite to the screen with an outline of the specified colour
--
function outline_sprite(n,col_outline,x,y,w,h,flip_x,flip_y)
  -- reset palette to black
  for c=1,15 do
    pal(c,col_outline)
  end
  -- draw outline
  for xx=-1,1 do
    for yy=-1,1 do
      spr(n,x+xx,y+yy,w,h,flip_x,flip_y)
    end
  end
  -- reset palette
  pal()
  -- draw final sprite
  spr(n,x,y,w,h,flip_x,flip_y)	
end