如何在C#/ .NET中从另一个中减去一个位图？

using System.Drawing;
using System.Drawing.Imaging;

public static Bitmap SubtractBitmaps(Bitmap bmp1, Bitmap bmp2)
{
    Bitmap result = new Bitmap(bmp1.Width, bmp1.Height);
    using (Graphics g = Graphics.FromImage(result))
    {
        g.Clear(Color.Transparent);
        g.DrawImage(bmp1, new Point(0, 0));
        g.DrawImage(bmp2, new Point(0, 0));
    }

    for (int x = 0; x< result.Width; x++)
    {
        for (int y = 0; y< result.Height; y++)
        {
            Color pixelColor = result.GetPixel(x, y);
            Color bmp2PixelColor = bmp2.GetPixel(x, y);
            int r = pixelColor.R - bmp2PixelColor.R;
            int g = pixelColor.G - bmp2PixelColor.G;
            int b = pixelColor.B - bmp2PixelColor.B;
            result.SetPixel(x, y, Color.FromArgb(r, g, b));
        }
    }

    return result;
}