def setup
  img = loadImage("fruit.png")
  image(img, 0, 0, width, height)
  d = pixelDensity
  halfImage = (4 * (width * d) * (height * d / 2)).to_i
  loadPixels
  (0...halfImage).each do |i|
    pixels[i + halfImage] = pixels[i]
  end
  updatePixels
end