i, j, px, py = string.find(result, "([0-9.]+),%s*([0-9.]+)")
px, py = math.floor(px+0.5), math.floor(py+0.5)

-- copy image

w, h = img.width, img.height
pixels = {}
for y = 0, h-1 do
  for x = 0, w-1 do
    pixels[y*w+x+1] = img.getInt(x, y)
  end
end

-- paint point

for y = math.max(py-1, 0), math.min(py+1, h-1) do
  for x = math.max(px-1, 0), math.min(px+1, w-1) do
    pixels[y*w+x+1] = 0xFF0000
  end
end