Рисование мышкой с пробелами

 private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
 
            Pen p = new Pen(y, 2);
            SolidBrush br = new SolidBrush(y);
            Point prevLocMouse = new Point(e.X, e.Y);
            Graphics gr;
            if (flag)
            {
                pictureBox1.BackColor = Color.White;
                pictureBox1.Image = SrcImg;
                gr = Graphics.FromImage(pictureBox1.Image);
                //gr = pictureBox1.CreateGraphics();
                gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                gr.FillRectangle(br, e.X, e.Y, trackBar1.Value, trackBar1.Value);
                Point mousePos = new Point(e.X, e.Y);
                gr.DrawLine(p, mousePos, prevLocMouse);
                prevLocMouse = mousePos;
                SrcImg = new Bitmap(pictureBox1.Image, pictureBox1.Width, pictureBox1.Height);
            }
        }
 
        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            flag = true;            
        }
 
        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            flag = false;
        }

public partial class Form1 : Form
{
    private static Pen pen = new Pen(Color.Blue, 2);
    private static List<Point> points = new List<Point>();
    public Form1()
    {
        InitializeComponent();
    }
 
    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        if (points == null || points.Count == 0)
        {
            return;
        }
        e.Graphics.DrawCurve(pen, points.ToArray());
    }
 
    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        points.Clear();
        points.Add(e.Location);
    }
 
    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button!=MouseButtons.Left)
        {
            return;
        }
        points.Add(e.Location);
        if (points.Count > 2)
        {
            pictureBox1.Refresh();
        }
    }
 
    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
        points.Add(e.Location);
        if (points.Count > 2)
        {
            pictureBox1.Refresh();
        }
    }
}