Apply tiles from a tileset based on their neighbors

bitwisetiles.p8

pico-8 cartridge // http://www.pico-8.com
version 16
__lua__
--init
_t=0
dirx={-1,1,0,0,1,1,-1,-1}
diry={0,0,-1,1,-1,1,1,-1}
tiles={16,8,15,7,12,4,11,3,14,6,13,5,10,2,9,0}
function _init()
	_upd=upd_game
	_drw=drw_game
end
-->8
--update
function _update()
	_t+=1
	_upd()
end
function upd_game()	
 if btnp(4) then
  gen_bitwise()
 end
 if btnp(5) then
  reload(0x2000,0x2000,0x1000)
 end
end


function gen_bitwise()


 for x=0,15 do
  for y=0,15 do
   local t,ct,nt = checktile(x,y),mget(x,y)

   for i=1,#tiles do
    if t < (i*16) then
     nt=tiles[i]
     break
    end
   end

   if nt > 0 and ct > 0 then
    mset(x,y,nt)
   end
  end
 end
end

function checktile(x,y)
	local sig,parity=0
	for i=1,8 do
		local dx,dy=x+dirx[i],y+diry[i]
		local t=mget(dx,dy)
		if t>0 then
			parity=0
		else
			parity=1
		end
		sig=bor(sig,shl(parity,8-i))
	end
	return sig
end
-->8
--draw
function _draw()
	_drw()
end

function drw_game()
	cls(1)
	map()
 printo("z to generate bitwise tiles",5, 5)
 printo("x to reset map",5,12)
end
-->8
--tools
function printo(str, x, y, c1, c2)
c1 = c1 or 7
c2 = c2 or 0

 for i=-1,1 do
  for j=-1,1 do
   print(str,x+i,y+j,c2)
  end
 end
 print(str,x,y,c1)
end

__gfx__
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__map__
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