An easy way to resize your game.

FreeRes.lua

--[[
    FreeRes - An easy way to resize your game.
     FreeRes is a library that makes adding multiple aspect ratio support to your game
     easily.
     It's been created to fill the hole that TLfres left after it became obsolete.
     Because of this its methods use the same names.
]]--
FreeRes = {} -- namespace

 local currentWidth, currentHeight, originalWidth, originalHeight, scale, scaleMultiplier, letterWidth, letterHeight, xLetter, yLetter

-- Sets up FreeRes, call on love.load() [and on resize]
--[[
param c = {w = currentScreenWidth, h = currentScrenHeight} (default = 800, 600)
param o = {w = originalScreenWidth, h = originalScrenHeight} (default = 800, 600)
]]--
function FreeRes.setScreen(c, o, scaleMultiplier)
  currentWidth = c.w or 800
  currentHeight = c.h or 600
  originalWidth = o.w or 800
  originalHeight = o.h or 600
  scaleMultiplier = scaleMultiplier or 1

  if currentWidth/currentHeight < originalWidth/originalHeight then
    scale = currentWidth/originalWidth
    xTranslate, yTranslate = 0, (currentHeight-(originalHeight*scale))/2
    letterWidth = love.graphics.getWidth()
    letterHeight = yTranslate
    xLetter = 0
    yLetter = yTranslate + originalHeight * scale
  elseif currentWidth/currentHeight > originalWidth/originalHeight then
    scale = currentHeight/originalHeight
    xTranslate, yTranslate = (currentWidth-(originalWidth*scale))/2, 0
    letterWidth = xTranslate
    letterHeight = love.graphics.getHeight()
    xLetter = xTranslate + originalWidth * scale
    yLetter = 0
  else xTranslate, yTranslate = 0, 0
    scale = currentWidth/originalWidth
    letterWidth, letterHeight = 0, 0
    xLetter, yLetter = 0, 0
  end

  scale = scale*scaleMultiplier
end

-- Transforms screen. Call at the beginning of love.draw()
function FreeRes.transform()
  love.graphics.push()
  love.graphics.translate(xTranslate, yTranslate)
  love.graphics.scale(scale, scale)
end

--Draw the letterbox. Call at the end of love.draw()
--[[
param color = {r, g, b, a} (defaults to black)
--]]
function FreeRes.letterbox(color)
  c = color or {0, 0, 0, 255}

  love.graphics.pop()
  love.graphics.setColor(c)
  -- Upper / Left letterbox
  love.graphics.rectangle("fill", 0, 0, letterWidth, letterHeight)

  -- Lower / Right letterbox
  love.graphics.rectangle("fill", xLetter, yLetter, letterWidth, letterHeight)
  love.graphics.setColor(255, 255, 255, 255)
end