彩色图像转换为黑白

 public Bitmap Convert(Bitmap OldBm)
        {
            Color c;
            int luma;
            Bitmap NewBm = new Bitmap(OldBm.Width, OldBm.Height);
            for (int y = 0; y < NewBm.Height; y++)
            {
                for (int x = 0; x < NewBm.Width; x++)
                {
                    c = OldBm.GetPixel(x, y);
                    luma = (int)(c.R * 0.3 + c.G * 0.59 + c.B * 0.11);
                    NewBm.SetPixel(x,y,Color.FromArgb(luma,luma,luma));
                }
            }
            return NewBm;
        }