love2d-tank/libs/sti/atlas.lua

---- Texture atlas complement for the Simple Tiled Implementation
-- @copyright 2022
-- @author Eduardo Hernández coz.eduardo.hernandez@gmail.com
-- @license MIT/X11

local module = {}

--- Create a texture atlas
-- @param files Array with filenames
-- @param sort If "size" will sort by size, or if "id" will sort by id
-- @param ids Array with ids of each file
-- @param pow2 If true, will force a power of 2 size
function module.Atlas(files, sort, ids, pow2)
	local function Node(x, y, w, h)
		return { x = x, y = y, w = w, h = h }
	end

	local function nextpow2(n)
		local res = 1
		while res <= n do
			res = res * 2
		end
		return res
	end

	local function loadImgs()
		local images = {}
		for i = 1, #files do
			images[i] = {}
			--images[i].name = files[i]
			if ids then
				images[i].id = ids[i]
			end
			images[i].img = love.graphics.newImage(files[i])
			images[i].w = images[i].img:getWidth()
			images[i].h = images[i].img:getHeight()
			images[i].area = images[i].w * images[i].h
		end
		if sort == "size" or sort == "id" then
			table.sort(images, function(a, b)
				return (a.area > b.area)
			end)
		end
		return images
	end

	--TODO: understand this func
	local function add(root, id, w, h)
		if root.left or root.right then
			if root.left then
				local node = add(root.left, id, w, h)
				if node then
					return node
				end
			end
			if root.right then
				local node = add(root.right, id, w, h)
				if node then
					return node
				end
			end
			return nil
		end

		if w > root.w or h > root.h then
			return nil
		end

		local _w, _h = root.w - w, root.h - h

		if _w <= _h then
			root.left = Node(root.x + w, root.y, _w, h)
			root.right = Node(root.x, root.y + h, root.w, _h)
		else
			root.left = Node(root.x, root.y + h, w, _h)
			root.right = Node(root.x + w, root.y, _w, root.h)
		end

		root.w = w
		root.h = h
		root.id = id

		return root
	end

	local function unmap(root)
		if not root then
			return {}
		end

		local tree = {}
		if root.id then
			tree[root.id] = {}
			tree[root.id].x, tree[root.id].y = root.x, root.y
		end

		local left = unmap(root.left)
		local right = unmap(root.right)

		for k, v in pairs(left) do
			tree[k] = {}
			tree[k].x, tree[k].y = v.x, v.y
		end
		for k, v in pairs(right) do
			tree[k] = {}
			tree[k].x, tree[k].y = v.x, v.y
		end

		return tree
	end

	local function bake()
		local images = loadImgs()

		local root = {}
		local w, h = images[1].w, images[1].h

		if pow2 then
			if w % 1 == 0 then
				w = nextpow2(w)
			end
			if h % 1 == 0 then
				h = nextpow2(h)
			end
		end

		repeat
			local node

			root = Node(0, 0, w, h)

			for i = 1, #images do
				node = add(root, i, images[i].w, images[i].h)
				if not node then
					break
				end
			end

			if not node then
				if h <= w then
					if pow2 then
						h = h * 2
					else
						h = h + 1
					end
				else
					if pow2 then
						w = w * 2
					else
						w = w + 1
					end
				end
			else
				break
			end
		until false

		local limits = love.graphics.getSystemLimits()
		if w > limits.texturesize or h > limits.texturesize then
			return "Resulting texture is too large for this system"
		end

		local coords = unmap(root)
		local map = love.graphics.newCanvas(w, h)
		love.graphics.setCanvas(map)
		--        love.graphics.clear()

		for i = 1, #images do
			love.graphics.draw(images[i].img, coords[i].x, coords[i].y)
			if ids then
				coords[i].id = images[i].id
			end
		end
		love.graphics.setCanvas()

		if sort == "ids" then
			table.sort(coords, function(a, b)
				return (a.id < b.id)
			end)
		end

		return { image = map, coords = coords }
	end

	return bake()
end

return module