TIC-80 outline

outline.lua

-- made for my Devtober2022 entry
-- you can read the corresponding devlog on: 
-- https://ko-fi.com/post/Eng-Devtober2020-2--Graphical-Enhancements-X8X3FKCIB
-- https://itch.io/jam/devtober-2022/topic/2406837/achies-devlog-shmup-game

function draw_outline(_spr,_x,_y,_bg,_clr)
  --palette address in memory
	local palette_map = 0x3ff0
	
  -- loop through colors and set all of them to the outline color.
	for c=1,15 do
		poke4(palette_map*2+c,_clr)
	end
	
  -- draw the sprite 4 times offset to the left-right up-down
	for i=_x-1,_x+1,1 do
		for j=_y-1,_y+1,1 do
			spr(_spr,i,j,_bg)
		end
	end	

   -- reset the palette
	for c=0,15 do
		poke4(palette_map*2+c,c)
	end
	
  -- draw the original sprite
	spr(_spr,_x,_y,_bg)

end