private void button9_Click(object sender, EventArgs e)
        {
            Bitmap b1 = (Bitmap)pictureBox1.Image;
            Bitmap b2 = (Bitmap)pictureBox2.Image;
            Color k;
            int prog = trackBar1.Value;
            int r, g, b;
            for (int x = 0; x < szer; x++)
            {
                for (int y = 0; y < wys; y++)
                {
                    k = b1.GetPixel(x, y);
                    r = k.R;
                    g = k.G;
                    b = k.B;
                    int a = (r + g + b) / 3;
                    if (a < prog)
                    {
                        k = Color.Black;
                    }
                    else
                        k = Color.White;

                    b2.SetPixel(x, y, k);
                }
            }
            pictureBox2.Refresh();
        }

private void trackBar1_Scroll(object sender, EventArgs e)
        {
            label1.Text = trackBar1.Value.ToString();
        }