Sharpen on a Bitmap using C#

I took Daniel’s answer and modified it for performance, by using BitmapData class, since using GetPixel/SetPixel is very expensive and inappropriate for performance-hungry systems. It works exactly the same as the previous solution and can be used instead.

   public static Bitmap Sharpen(Bitmap image)
    {
        Bitmap sharpenImage = (Bitmap)image.Clone();

        int filterWidth = 3;
        int filterHeight = 3;
        int width = image.Width;
        int height = image.Height;

        // Create sharpening filter.
        double[,] filter = new double[filterWidth, filterHeight];
        filter[0, 0] = filter[0, 1] = filter[0, 2] = filter[1, 0] = filter[1, 2] = filter[2, 0] = filter[2, 1] = filter[2, 2] = -1;
        filter[1, 1] = 9;

        double factor = 1.0;
        double bias = 0.0;

        Color[,] result = new Color[image.Width, image.Height];

        // Lock image bits for read/write.
        BitmapData pbits = sharpenImage.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

        // Declare an array to hold the bytes of the bitmap.
        int bytes = pbits.Stride * height;
        byte[] rgbValues = new byte[bytes];

        // Copy the RGB values into the array.
        System.Runtime.InteropServices.Marshal.Copy(pbits.Scan0, rgbValues, 0, bytes);

        int rgb;
        // Fill the color array with the new sharpened color values.
        for (int x = 0; x < width; ++x)
        {
            for (int y = 0; y < height; ++y)
            {
                double red = 0.0, green = 0.0, blue = 0.0;

                for (int filterX = 0; filterX < filterWidth; filterX++)
                {
                    for (int filterY = 0; filterY < filterHeight; filterY++)
                    {
                        int imageX = (x - filterWidth / 2 + filterX + width) % width;
                        int imageY = (y - filterHeight / 2 + filterY + height) % height;

                        rgb = imageY * pbits.Stride + 3 * imageX;

                        red += rgbValues[rgb + 2] * filter[filterX, filterY];
                        green += rgbValues[rgb + 1] * filter[filterX, filterY];
                        blue += rgbValues[rgb + 0] * filter[filterX, filterY];
                    }
                    int r = Math.Min(Math.Max((int)(factor * red + bias), 0), 255);
                    int g = Math.Min(Math.Max((int)(factor * green + bias), 0), 255);
                    int b = Math.Min(Math.Max((int)(factor * blue + bias), 0), 255);

                    result[x, y] = Color.FromArgb(r, g, b);
                }
            }
        }

        // Update the image with the sharpened pixels.
        for (int x = 0; x < width; ++x)
        {
            for (int y = 0; y < height; ++y)
            {
                rgb = y * pbits.Stride + 3 * x;

                rgbValues[rgb + 2] = result[x, y].R;
                rgbValues[rgb + 1] = result[x, y].G;
                rgbValues[rgb + 0] = result[x, y].B;
            }
        }

        // Copy the RGB values back to the bitmap.
        System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, pbits.Scan0, bytes);
        // Release image bits.
        sharpenImage.UnlockBits(pbits);

        return sharpenImage;
    }