A Tilemap class. Unsure if the collision code works.

Sheet.lua

Sheet = class("Sheet")

function Sheet:initialize(img, tileWidth, tileHeight)
  self.x = 0
  self.y = 0
  self.image = img
  self.tw = tileWidth
  self.th = tileHeight
  self.quads = {}
  
  local i = 1
  local iw, ih = img:getWidth(), img:getHeight()
  
  for y = 0, ih, tileHeight do
    for x = 0, iw, tileWidth do
      self.quads[i] = love.graphics.newQuad(x, y, tileWidth, tileHeight, iw, ih)
      i = i + 1
    end
  end
end

Tilemap.lua

Tilemap = class("Tilemap", Sheet)

function Tilemap:initialize(img, columns, rows, tileWidth, tileHeight, solid)
  Sheet.initialize(self, img, tileWidth, tileHeight)
  self.cols = columns 
  self.rows = rows
  self.batch = love.graphics.newSpriteBatch(img)
  self.solid = solid
  if solid then self.map = {} end
end

function Tilemap:draw()
  love.graphics.draw(self.batch, self.x, self.y)
end

function Tilemap:set(x, y, index)
  if index > 0 then self.batch:addq(self.quads[index], x * self.tw, y * self.th) end
  if self.solid then self.map[y * self.cols + x] = index > 0 end
end

function Tilemap:load(t)
  local i = 1
  
  for y = 0, self.rows - 1 do
    for x = 0, self.cols - 1 do
      if t[i] > 0 then self:set(x, y, t[i]) end
      i = i + 1
    end
  end
end

function Tilemap:collideRect(x, y, width, height)
  x = math.floor((x - self.x) / self.tw)
  y = math.floor((y - self.y) / self.th)
  width = math.floor(width / self.tw)
  height = math.floor(height / self.th)
  
  for ix = x, width - 1 do
    for iy = y, height - 1 do
      if self.map[iy * self.cols + ix] then return true end
    end
  end
  
  return false
end