Sobel filter kernel of large size

Question

I am using a sobel filter of size 3x3 to calculate the image derivative. Looking at some articles on the internet, it seems that kernels for sobel filter for size 5x5 and 7x

Answer 1

I quickly hacked an algorithm to generate a Sobel kernel of any odd size > 1, based on the examples given by @Paul R:

    public static void CreateSobelKernel(int n, ref float[][] Kx, ref float[][] Ky)
    {
        int side = n * 2 + 3;
        int halfSide = side / 2;
        for (int i = 0; i < side; i++)
        {
            int k = (i <= halfSide) ? (halfSide + i) : (side + halfSide - i - 1);
            for (int j = 0; j < side; j++)
            {
                if (j < halfSide)
                    Kx[i][j] = Ky[j][i] = j - k;
                else if (j > halfSide)
                    Kx[i][j] = Ky[j][i] = k - (side - j - 1);
                else
                    Kx[i][j] = Ky[j][i] = 0;
            }
        }
    }

Hope it helps.