filter

private void btn_Filter_Click(object sender, EventArgs e)
{
    String lpf = (String)comboBox1.SelectedItem;
    String hpf = (String)comboBox2.SelectedItem;
    String banding = (String)comboBox3.SelectedItem;
    int[] xt = new int[10];
    objBitmap10 = new Bitmap(objBitmap1);
    for (int x = 1; x < objBitmap1.Width - 1; x++)
        for (int y = 1; y < objBitmap1.Height - 1; y++)
        {
            Color w1 = objBitmap1.GetPixel(x - 1, y - 1);
            Color w2 = objBitmap1.GetPixel(x - 1, y);
            Color w3 = objBitmap1.GetPixel(x - 1, y + 1);
            Color w4 = objBitmap1.GetPixel(x, y - 1);
            Color w5 = objBitmap1.GetPixel(x, y);
            Color w6 = objBitmap1.GetPixel(x, y + 1);
            Color w7 = objBitmap1.GetPixel(x + 1, y - 1);
            Color w8 = objBitmap1.GetPixel(x + 1, y);
            Color w9 = objBitmap1.GetPixel(x + 1, y + 1);
            xt[1] = w1.R; xt[2] = w2.R;
            xt[3] = w3.R; xt[4] = w4.R;
            xt[5] = w5.R; xt[6] = w6.R;
            xt[7] = w7.R; xt[8] = w8.R;
            xt[9] = w9.R;
            int xlpf, xhpf, xbanding;
            switch (lpf)
            {
                case "Filter Rata-Rata":
                    xlpf = rataFilter(xt);
                    break;
                case "Filter Gaussian":
                    xlpf = gaussianFilter(xt);
                    break;
                case "Filter Median":
                    xlpf = medianFilter(xt);
                    break;
                default:
                    xlpf = rataFilter(xt);
                    break;
            }
            switch (hpf)
            {
                case "Sobel":
                    xhpf = sobelFilter(xt);
                    break;
                case "Prewitt":
                    xhpf = prewittFilter(xt);
                    break;
                case "Laplacian":
                    xhpf = laplacianFilter(xt);
                    break;
                default:
                    xhpf = sobelFilter(xt);
                    break;
            }
            switch (banding)
            {
                case "2:1":
                    xbanding = banding1(xt);
                    break;
                case "1:2":
                    xbanding = banding2(xt);
                    break;
                default:
                    xbanding = banding1(xt);
                    break;
            }
            int xb = xlpf + xhpf;
            if (xb < 0) xb = -xb;
            if (xb > 255) xb = 255;
            Color wb = Color.FromArgb(xb, xb, xb);
            objBitmap10.SetPixel(x, y, wb);
        }
    pb_Prak11.Image = objBitmap10;
}

public int sobelFilter(int[] x)
{
    int xv = (int)(-x[1] - 2 * x[2] - x[3] + x[7] + 2 * x[8] + x[9]);
    int xh = (int)(x[1] + 2 * x[4] + x[7] - x[3] - 2 * x[6] - x[9]);
    return (xv + xh);
}
public int prewittFilter(int[] x)
{
    int xv = (int)(-x[1] - x[2] - x[3] + x[7] + x[8] + x[9]);
    int xh = (int)(x[1] + x[4] + x[7] - x[3] - x[6] - x[9]);
    return (xv + xh);
}
public int laplacianFilter(int[] x)
{
    int xb = (int)(x[1]- 2 * x[2] + x[3] - 2 * x[4] + 4 * x[5] - 2 * x[6] + x[7] - 2 * x[8] + x[9]);
    return (xb);
}
public int rataFilter(int[] x)
{
    int xb = (int)((x[1] + x[2] + x[3] + x[4] + x[5] + x[6] + x[7] + x[8]) / 9);
    return xb;
}
public int gaussianFilter(int[] x)
{
    int xb = (int)(xt[1] * x[1] + xt[2] * x[2] + xt[3] * x[3]);
    xb = (int)(xb + xt[4] * x[4] + xt[5] * x[5] + xt[6] * x[6]);
    xb = (int)(xb + xt[7] * x[7] + xt[8] * x[8] + xt[9] * x[9]);
    if (xb < 0) xb = 0;
    if (xb > 255) xb = 255;
    return (xb);
}
public int medianFilter(int[] x)
{
    int max;
    int temp = 0;
    for (int d = 1; d <= 9; d++)
    {
        if (xt[d] < xt[d - 1])
        {
            max = (int)xt[d - 1];
            xt[d - 1] = temp;
            temp = (int)xt[d];
            xt[d] = xt[d - 1];
        }
        else
        {
            continue;
        }
    }
    int xb = (int)xt[5];
    if (xb < 0) xb = 0;
    if (xb > 255) xb = 255;
    return (xb);
}
public int banding1(int[] x)
{
    int xb = (2 * xt[1] + xt[2] + xt[3]) /2;
    return xb;
}
public int banding2(int[] x)
{
    int xb = (xt[1]+2*xt[2]+2*xt[3])/3;
    return xb;
}