C#实现hough直线检测

以下是使用C#实现Hough直线检测的步骤：

1.读取图像并将其转换为灰度图像。

Bitmap bmp = new Bitmap("image.jpg");
Bitmap grayImage = new Bitmap(bmp.Width, bmp.Height);

for (int i = 0; i < bmp.Width; i++)
{
    for (int j = 0; j < bmp.Height; j++)
    {
        Color c = bmp.GetPixel(i, j);
        int gray = (int)(c.R * 0.3 + c.G * 0.59 + c.B * 0.11);
        grayImage.SetPixel(i, j, Color.FromArgb(gray, gray, gray));
    }
}

2.计算图像中每个像素的边缘强度。

Bitmap edgeImage = new Bitmap(grayImage.Width, grayImage.Height);

for (int i = 1; i < grayImage.Width - 1; i++)
{
    for (int j = 1; j < grayImage.Height - 1; j++)
    {
        int gx = (grayImage.GetPixel(i + 1, j - 1).R + 2 * grayImage.GetPixel(i + 1, j).R + grayImage.GetPixel(i + 1, j + 1).R)
            - (grayImage.GetPixel(i - 1, j - 1).R + 2 * grayImage.GetPixel(i - 1, j).R + grayImage.GetPixel(i - 1, j + 1).R);
        int gy = (grayImage.GetPixel(i - 1, j + 1).R + 2 * grayImage.GetPixel(i, j + 1).R + grayImage.GetPixel(i + 1, j + 1).R)
            - (grayImage.GetPixel(i - 1, j - 1).R + 2 * grayImage.GetPixel(i, j - 1).R + grayImage.GetPixel(i + 1, j - 1).R);
        int g = (int)Math.Sqrt(gx * gx + gy * gy);
        edgeImage.SetPixel(i, j, Color.FromArgb(g, g, g));
    }
}

3.在Hough空间中进行累加。

int[,] houghSpace = new int[180, (int)Math.Sqrt(grayImage.Width * grayImage.Width + grayImage.Height * grayImage.Height)];

for (int i = 0; i < edgeImage.Width; i++)
{
    for (int j = 0; j < edgeImage.Height; j++)
    {
        if (edgeImage.GetPixel(i, j).R > 128)
        {
            for (int theta = 0; theta < 180; theta++)
            {
                double r = i * Math.Cos(theta * Math.PI / 180) + j * Math.Sin(theta * Math.PI / 180);
                houghSpace[theta, (int)r]++;
            }
        }
    }
}

4.在Hough空间中找到峰值点。

List<Point> lines = new List<Point>();

for (int i = 0; i < 180; i++)
{
    for (int j = 0; j < houghSpace.GetLength(1); j++)
    {
        if (houghSpace[i, j] > 100)
        {
            bool isMax = true;
            for (int m = i - 10; m <= i + 10; m++)
            {
                for (int n = j - 10; n <= j + 10; n++)
                {
                    if (m >= 0 && m < 180 && n >= 0 && n < houghSpace.GetLength(1))
                    {
                        if (houghSpace[m, n] > houghSpace[i, j])
                        {
                            isMax = false;
                            break;
                        }
                    }
                }
                if (!isMax)
                {
                    break;
                }
            }
            if (isMax)
            {
                lines.Add(new Point(i, j));
            }
        }
    }
}

5.将检测到的直线绘制到原始图像上。

Graphics g = Graphics.FromImage(bmp);
Pen pen = new Pen(Color.Red, 2);

foreach (Point p in lines)
{
    double theta = p.X * Math.PI / 180;
    double r = p.Y;
    int x0 = 0;
    int y0 = (int)(r / Math.Sin(theta));
    int x1 = bmp.Width;
    int y1 = (int)((r - x1 * Math.Cos(theta)) / Math.Sin(theta));
    g.DrawLine(pen, x0, y0, x1, y1);
}