锐化滤镜-没有效果

以下例程仅锐化8位索引灰度。

这段代码似乎对输入图像没有影响。也就是说，输入的和输出的是一样的。

如果我增加strength的值，图像似乎变得更暗，但是，从未过滤。

可能出了什么问题?

我使用下面的内核，

double[,] _numericalKernel = new double[,] 
                             { { -1, -1, -1, }, 
                               { -1,  9, -1, }, 
                               { -1, -1, -1, }, };

下面是我锐化的源代码，

    public static Bitmap NonfftSharpen(Bitmap image, double[,] mask, double strength)
    {
        Bitmap bitmap = (Bitmap)image.Clone();
        if (bitmap != null)
        {
            int width = bitmap.Width;
            int height = bitmap.Height;
            if (mask.GetLength(0) != mask.GetLength(1))
            {
                throw new Exception("_numericalKernel dimensions must be same");
            }
            // Create sharpening filter.
            int filterSize = mask.GetLength(0);
            double[,] filter = (double[,])mask.Clone();
            int channels = sizeof(byte);
            double bias = 1.0 - strength;
            double factor = strength / 16.0;
            int halfOfFilerSize = filterSize / 2;
            byte[,] result = new byte[bitmap.Width, bitmap.Height];
            // Lock image bits for read/write.
            BitmapData bitmapData = bitmap.LockBits(new Rectangle(0, 0, width, height),
                                                        ImageLockMode.ReadWrite,
                                                        PixelFormat.Format8bppIndexed);
            // Declare an array to hold the bytes of the bitmap.
            int memorySize = bitmapData.Stride * height;
            byte[] memory = new byte[memorySize];
            // Copy the RGB values into the local array.
            Marshal.Copy(bitmapData.Scan0, memory, 0, memorySize);
            int rgb;
            // Fill the color array with the new sharpened color values.
            for (int y = halfOfFilerSize; y < height - halfOfFilerSize; y++)
            {
                for (int x = halfOfFilerSize; x < width - halfOfFilerSize; x++)
                {
                    for (int filterY = 0; filterY < filterSize; filterY++)
                    {
                        double grayShade = 0.0;
                        for (int filterX = 0; filterX < filterSize; filterX++)
                        {
                            int imageX = (x - halfOfFilerSize + filterX + width) % width;
                            int imageY = (y - halfOfFilerSize + filterY + height) % height;
                            rgb = imageY * bitmapData.Stride + channels * imageX;
                            grayShade += memory[rgb + 0] * filter[filterX, filterY];
                        }
                        rgb = y * bitmapData.Stride + channels * x;
                        int b = Math.Min(Math.Max((int)(factor * grayShade + (bias * memory[rgb + 0])), 0), 255);
                        result[x, y] = (byte)b;
                    }
                }
            }
            // Update the image with the sharpened pixels.
            for (int x = halfOfFilerSize; x < width - halfOfFilerSize; x++)
            {
                for (int y = halfOfFilerSize; y < height - halfOfFilerSize; y++)
                {
                    rgb = y * bitmapData.Stride + channels * x;
                    memory[rgb + 0] = result[x, y];
                }
            }
            // Copy the RGB values back to the bitmap.
            Marshal.Copy(memory, 0, bitmapData.Scan0, memorySize);
            // Release image bits.
            bitmap.UnlockBits(bitmapData);
            return bitmap;
        }
        else
        {
            throw new Exception("input image can't be null");
        }
    }

    public static Bitmap NonfftSharpen(Bitmap image, double[,] mask, double strength)
    {
        Bitmap bitmap = (Bitmap)image.Clone();
        if (bitmap != null)
        {
            int width = bitmap.Width;
            int height = bitmap.Height;
            if (mask.GetLength(0) != mask.GetLength(1))
            {
                throw new Exception("_numericalKernel dimensions must be same");
            }
            // Create sharpening filter.
            int filterSize = mask.GetLength(0);
            double[,] filter = (double[,])mask.Clone();
            int channels = sizeof(byte);
            double bias = 0.0; // 1.0 - strength;
            double factor = 1.0; // strength / 16.0;
            byte[,] result = new byte[bitmap.Width, bitmap.Height];
            // Lock image bits for read/write.
            BitmapData bitmapData = bitmap.LockBits(new System.Drawing.Rectangle(0, 0, width, height),
                                                        ImageLockMode.ReadWrite,
                                                        System.Drawing.Imaging.PixelFormat.Format8bppIndexed);
            // Declare an array to hold the bytes of the bitmap.
            int memorySize = bitmapData.Stride * height;
            byte[] memory = new byte[memorySize];
            // Copy the RGB values into the local array.
            Marshal.Copy(bitmapData.Scan0, memory, 0, memorySize);
            int pixel;
            // Fill the color array with the new sharpened color values.
            for (int y = 0; y < height; y++)
            {
                for (int x = 0; x < width; x++)
                {
                    double grayShade = 0.0;
                    for (int filterY = 0; filterY < filterSize; filterY++)
                    {

                        for (int filterX = 0; filterX < filterSize; filterX++)
                        {
                            int imageX = (x - filterSize / 2 + filterX + width) % width;
                            int imageY = (y - filterSize / 2 + filterY + height) % height;
                            pixel = imageY * bitmapData.Stride + channels * imageX;
                            grayShade += memory[pixel] * filter[filterX, filterY];
                        }
                        int newPixel = Math.Min(Math.Max((int)(factor * grayShade + bias), 0), 255);
                        result[x, y] = (byte)newPixel;
                    }
                }
            }
            // Update the image with the sharpened pixels.
            for (int x = 0; x < width; x++)
            {
                for (int y = 0; y < height; y++)
                {
                    pixel = y * bitmapData.Stride + channels * x;
                    memory[pixel] = result[x, y];
                }
            }
            // Copy the values back to the bitmap.
            Marshal.Copy(memory, 0, bitmapData.Scan0, memorySize);
            // Release image bits.
            bitmap.UnlockBits(bitmapData);
            return bitmap;
        }
        else
        {
            throw new Exception("input image can't be null");
        }
    }