Pico-8 Sprite with color outline

pico8_outline.p8

-- https://ko-fi.com/achiegamedev

-- draw the myspr sprite at x and y with a 1 pixel
-- wide outline of clr. if clr is not given on the call
-- default 7 is used instead. thickness is how thick the outline
-- should be in pixels. defaults to 1 if none given
function draw_outline(myspr, x, y, clr, thickness, x_size, y_size, flip_h, flip_v)
    -- nil check for few parameters so you can
    -- call much simple versions of the function, see first example in draw
    -- nil is false if checked for boolean so flip_h and flip_v can stay nil
    if (clr == nil) clr = 7
    if (thickness == nil) thickness = 1 
    if (x_size == nil) x_size = 1    
    if (y_size == nil) y_size = 1 
    
    -- set color palette to outline
    for i=1,15,1 do
        pal(i, clr)
    end

    -- handle black outline transparency issues
    if clr == 0 then
        palt(0, false)
    end

    -- draw the sprite 9 times by 1-1 offsets
    -- in each direction. the created blob is 
    -- which is the sprite's outline 
    for i=-thickness,thickness do
        for j=-thickness,thickness do
            spr(myspr, x-i, y-j, x_size, y_size, flip_h, flip_v)
        end
    end

    -- reset black color transparency
    if clr == 0 then
        palt(0, true)
    end

    -- reset color palette, if you are using
    -- a custom palette reset to that
    pal()

    -- draw the original sprite in the middle
    -- which causes the outline effect
    spr(myspr, x, y, x_size, y_size, flip_h, flip_v)
end

function _draw()
	cls()
	
	-- draw a simple 8x8 sprite
	-- with outline color white = 7
	draw_outline(1,10,10,7)
	
	-- draw a simple 8x8 sprite
	-- with outline color white = 7
	-- horizontal flipped
	-- we need the thickness and
	-- the size as well for the 
	-- params, so 1,1,1 where first
	-- is outline thickness second
	-- two is sprite tile size like
	-- normal spr(), then we can flip
	-- with a true. Same sprite as first
	-- but flipped
	draw_outline(1,10,20,7,1,1,1, true)
	
	
	
	
	-- draw a 16x16 sprite,
	-- outline color 9, two wide
	-- flipped horizontal
	draw_outline(2,10,60,9,2,2,2,true)
end