creating unique GUIDs for Aseprite files

aseprite-guid.lua

-- This creates proper GUIDs for Aseprite files so the game can load them.

-- To Use:
-- 1) Open Aseprite and go to File -> Scripts -> Open Scripts Folder and place this file there
-- 2) Restart Aseprite
-- 3) Run this script when you save an Aseprite file and it will automatically create
--	  GUIDs for the sprite along with every slice

-- More Info: https://www.aseprite.org/docs/scripting/

local numbers = "0123456789ABCDEF"
local output = {}
local updated = 0

function rndl(n)
	local result = ""
	for i = 1,n,1 do
		local index = math.random(1, 16)
		result = result .. numbers:sub(index, index)
	end

	return result
end

function makeguid()
    return rndl(8) .. "-" .. rndl(4) .. "-" .. rndl(4) .. "-" .. rndl(4) .. "-" .. rndl(12)
end

function checkguid(obj, type)
	if obj.data:len() < 41 or obj.data:sub(0, 4) ~= "GUID" then
		local guid = makeguid()
		obj.data = "GUID:" .. guid
		obj.color = Color{ r=215, g=123, b=186, a=255 }
		table.insert(output, "Set " .. type .. " '" .. obj.name .. "' GUID to '" .. guid .. "'")
		updated = updated + 1
	end
end

local sprite = app.activeSprite

-- Set a GUID on the Sprite's bottom Layer
checkguid(sprite.layers[1], "Layer")

-- Set a GUID to each Slice
for i,slice in ipairs(sprite.slices) do
	checkguid(slice, "Slice")
end

-- Tell the User if any GUIDs were updated
if updated > 0 then
	app.alert{ title="Updated " .. updated .. " GUIDs", text=output }
end

-- Save the File
app.command.SaveFile()