使用C#锐化位图

Question

我想在图像上放置一个锐化滤镜.我找到了一个简短教程的网站.我试着在C#中这样做,所以这是我的代码.无论如何,我试图找出它为什么不起作用.我不知道我做错了什么,如果是的话,请告诉我该怎么做才能让它按原样运作.谢谢

        public static Bitmap sharpen(Bitmap image)
    {
        Bitmap sharpenImage = new Bitmap(image.Width, image.Height);

        int filterWidth = 3;
        int filterHeight = 3;
        int w = image.Width;
        int h = image.Height;

        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];

        for (int x = 0; x < w; ++x)
        {
            for (int y = 0; y < h; ++y)
            {
                double red = 0.0, green = 0.0, blue = 0.0;
                Color imageColor = image.GetPixel(x, y);

                for (int filterX = 0; filterX < filterWidth; filterX++)
                {
                    for (int filterY = 0; filterY < filterHeight; filterY++)
                    {
                        int imageX = (x - filterWidth / 2 + filterX + w) % w;
                        int imageY = (y - filterHeight / 2 + filterY + h) % h;
                        red += imageColor.R * filter[filterX, filterY];
                        green += imageColor.G * filter[filterX, filterY];
                        blue += imageColor.B * 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);
                }
            }
        }
        for (int i = 0; i < w; ++i)
        {
            for (int j = 0; j < h; ++j)
            {
                sharpenImage.SetPixel(i, j, result[i, j]);
            }
        }
        return sharpenImage;
    }

Answer 1

public static Bitmap sharpen(Bitmap image)
{
    Bitmap sharpenImage = new Bitmap(image.Width, image.Height);

    int filterWidth = 3;
    int filterHeight = 3;
    int w = image.Width;
    int h = image.Height;

    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];

    for (int x = 0; x < w; ++x)
    {
        for (int y = 0; y < h; ++y)
        {
            double red = 0.0, green = 0.0, blue = 0.0;

//=====[REMOVE LINES]========================================================
// Color must be read per filter entry, not per image pixel.
            Color imageColor = image.GetPixel(x, y);
//===========================================================================

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

//=====[INSERT LINES]========================================================
// Get the color here - once per fiter entry and image pixel.
                    Color imageColor = image.GetPixel(imageX, imageY);
//===========================================================================

                    red += imageColor.R * filter[filterX, filterY];
                    green += imageColor.G * filter[filterX, filterY];
                    blue += imageColor.B * 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);
            }
        }
    }
    for (int i = 0; i < w; ++i)
    {
        for (int j = 0; j < h; ++j)
        {
            sharpenImage.SetPixel(i, j, result[i, j]);
        }
    }
    return sharpenImage;
}

Answer 2

我采用了Daniel的答案,并通过使用BitmapData类对其性能进行了修改,因为使用GetPixel/SetPixel非常昂贵且不适合需要高性能的系统.它的工作原理与之前的解决方案完全相同,可以代替使用.

   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;
    }

Answer 3

这将产生更柔和的锐化效果.如果需要,您可以扩展滤镜阵列,或者将16更改为更大的滤镜阵列,但我发现这并不像您拥有的那样苛刻.

const int filterWidth = 5;
const int filterHeight = 5;

double[,] filter = new double[filterWidth,filterHeight] {
    { -1, -1, -1, -1, -1 },
    { -1,  2,  2,  2, -1 },
    { -1,  2,  16,  2, -1 },
    { -1,  2,  2,  2, -1 },
    { -1, -1, -1, -1, -1 }
};

double factor = 1.0 / 16.0;