-- ImageData test on love2d

function make_gradation(imgdata)
  local w, h = imgdata:getDimensions()
  local x, y
  for y = 0, (h - 1) do
    for x = 0, (w - 1) do
      local r, g, b, a
      r = x / (w - 1)
      g = y / (h - 1)
      b = (x / ((w - 1) / 4)) % 1.0
      a = (y / ((h - 1) / 4)) % 1.0
      imgdata:setPixel(x, y, r, g, b, a)
    end
  end
end

function brighten(x, y, r, g, b, a)
  r = math.min(r * 1.5, 1.0)
  g = math.min(g * 1.5, 1.0)
  b = math.min(b * 1.5, 1.0)
  return r, g, b, a
end

function darken(x, y, r, g, b, a)
  r = math.max(r * 0.75, 0.0)
  g = math.max(g * 0.75, 0.0)
  b = math.max(b * 0.75, 0.0)
  return r, g, b, a
end

function love.load()
  love.graphics.setDefaultFilter("nearest", "nearest")
  local w, h = love.graphics.getDimensions()

  imgdata = love.image.newImageData(w, h)
  make_gradation(imgdata)

  img = love.graphics.newImage(imgdata)
end

function love.update(dt)
end

function love.draw()
  love.graphics.clear(0, 0, 0, 1)

  love.graphics.setColor(1, 1, 1, 1)
  love.graphics.draw(img, 0, 0)

  love.graphics.print("Hit Up/Down key", 2, 20)
  love.graphics.print("FPS: " .. tostring(love.timer.getFPS()), 2, 2)
end

function love.keypressed(key, isrepeat)
  if key == "escape" then
    -- ESC key to exit
    love.event.quit()
  elseif key == "up" then
    imgdata:mapPixel(brighten)
    img:replacePixels(imgdata)
  elseif key == "down" then
    imgdata:mapPixel(darken)
    img:replacePixels(imgdata)
  end
end