6. 影像處理之邊緣偵測實作

這題真的蠻有趣的，卷積邊緣偵測操作

# 按像素操作圖片要用 BitMap (該class繼承 Image)

灰階轉換

private void button3_Click(object sender, EventArgs e)
{
    var img = (Bitmap)pictureBox1.Image;
    Bitmap map = new Bitmap(img.Width, img.Height);

    for (int x = 0; x < img.Width; x++)
    {
        for (int y = 0; y < img.Height; y++)
        {
            var color = img.GetPixel(x, y);
            int gay = (int)(color.R * 0.3 + color.G * 0.59 + color.B * 0.11);
            map.SetPixel(x, y, Color.FromArgb(gay, gay, gay));
        }
    }
    pictureBox2.Image = map;
}

邊緣偵測

private void button4_Click(object sender, EventArgs e)
{
    button3.PerformClick();
    var img = (Bitmap)pictureBox2.Image;
    int[,] input = new int[img.Width, img.Height];
    for (int x = 0; x < img.Width; x++)
        for (int y = 0; y < img.Height; y++) input[x, y] = img.GetPixel(x, y).R;
    int[,] gx = { { -1, 0, 1 }, { -2, 0, 2 }, { -1, 0, 1 } };
    int[,] gy = { { -1, -2, -1 }, { 0, 0, 0 }, { 1, 2, 1 } };

    int[,] ox公牛 = do捲機(input, gx);
    int[,] oyoyoy = do捲機(input, gy);

    var out破 = new Bitmap(ox公牛.GetLength(0), ox公牛.GetLength(1));
    for (int x = 0; x < ox公牛.GetLength(0); x++)
    {
        for (int y = 0; y < ox公牛.GetLength(1); y++)
        {
            int gray = (int)Math.Sqrt(ox公牛[x, y] * ox公牛[x, y] + oyoyoy[x, y] * oyoyoy[x, y]);
            if (gray > 255) gray = 255;
            out破.SetPixel(x, y, Color.FromArgb(gray, gray, gray));
        }
    }
    pictureBox2.Image = out破;
}

private int[,] do捲機(int[,] input, int[,] gx)
{
    int[,] output = new int[input.GetLength(0) - 2, input.GetLength(1) - 2];
    for (int x = 1; x < input.GetLength(0) - 1; x++)
    {
        for (int y = 1; y < input.GetLength(1) - 1; y++)
        {
            int sum = 0;
            for (int i = 0; i < 3; i++)
            {
                for (int j = 0; j < 3; j++)
                {
                    sum += gx[i, j] * input[x - 1 + i, y - 1 + j];
                }
            }
            output[x - 1, y - 1] = sum;
        }
    }
    return output;
}