get("#372") -- getContrast

brightnessThreshold = 0.55

-- convert pixel by pixel

w, h = img.width, img.height
pixels = {}
for y = 0, h-1 do
  for x = 0, w-1 do
    b = bright(rgb(img.getInt(x, y)))
    pixels[y*w+x+1] = b >= brightnessThreshold and -1 or 0
  end
end