[C#] 이미지를 흑백으로 바꾸기!

private Bitmap grayScale(Bitmap basebit)
{
    Bitmap newbit = new Bitmap(basebit.Width, basebit.Height);
    Graphics g = Graphics.FromImage(newbit);
    ColorMatrix cMatrix = new ColorMatrix(
        new float[][]
        {
            new float[] {.3f, .3f, .3f, 0, 0},
            new float[] {.59f, .59f, .59f, 0, 0},
            new float[] {.11f, .11f, .11f, 0, 0},
            new float[] {0, 0, 0, 1, 0},
            new float[] {0, 0, 0, 0, 1}
     });
    ImageAttributes attributes = new ImageAttributes();
    attributes.SetColorMatrix(cMatrix);
    g.DrawImage(basebit, new Rectangle(0, 0, basebit.Width, basebit.Height), 0, 0, basebit.Width, basebit.Height, GraphicsUnit.Pixel, attributes);
    g.Dispose();
    return newbit;
}