public static void Main(string[] args)
        {
            Stopwatch s = new Stopwatch();
            s.Start();

            while(true) {
                long start = s.ElapsedMilliseconds;

                Bitmap b = new Bitmap(1280, 720);

                BitmapData bData = b.LockBits(
                    new Rectangle(Point.Empty, b.Size),
                    ImageLockMode.ReadWrite,
                    PixelFormat.Format24bppRgb);

                int numBytes = Math.Abs(bData.Stride) * b.Height;

                byte[] rgbValues = new byte[numBytes];

                for(int i = 2; i < numBytes - 2; i += 3) {
                    if(0.3 * rgbValues[i] + 0.3 * rgbValues[i + 1] + 0.4 * rgbValues[i + 2] < 0.4) {
                        rgbValues[i] = 255;
                        rgbValues[i + 1] = 0;
                        rgbValues[i + 2] = 0;
                    }
                }

                System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, bData.Scan0, numBytes);

                b.UnlockBits(bData);

                b.Save("huy.png");

                Console.WriteLine("{0:F3}", (s.ElapsedMilliseconds - start) / 1000.0);
            }
        }