如何在将鼠标移到pictureBox1上时自动在pictureBox2上绘制点？

Question

private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                points.Add(new PointF(e.X * xFactor, e.Y * yFactor));
                pictureBox2.Invalidate();
                label5.Visible = true;
                label5.Text = String.Format("X: {0}; Y: {1}", e.X, e.Y);
                counter += 1;
                label6.Visible = true;
                label6.Text = counter.ToString();
            }
        }

         private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        label4.Visible = true;
        label4.Text = String.Format("X: {0}; Y: {1}", e.X, e.Y);
        if (panning)
        {
            movingPoint = new Point(e.Location.X - startingPoint.X,
                                    e.Location.Y - startingPoint.Y);
            pictureBox1.Invalidate();
        }
    }

        private void pictureBox2_Paint(object sender, PaintEventArgs e)
        {
            Pen p;
            p = new Pen(Brushes.Green);
            foreach (PointF pt in points)
            {
                e.Graphics.FillEllipse(Brushes.Red, pt.X, pt.Y, 3f, 3f);
            }

            for (int i = 0; i < points.Count - 1; i++)
            {
                if (points.Count > 1)
                {
                    e.Graphics.DrawLine(p, points[i].X, points[i].Y, points[i+1].X, points[i+1].Y);
                }
            }

            if (checkBox2.Checked)
            {

            }
        }

I added a new checkBox2 and in the paint event of checkBox2 i want to make that if its checked if i just move the mouse over the pictureBox1 area without clicking anything it will draw a line on pictureBox2 a route of where the mouse is moving in pictureBox1.

And ever X pixels i move the mouse it will create a point in Green color on this line.

Answer 1

You can use a GraphicsPath to save all the points mouse is over, that's way the drawing can be better than using some List or Array to store the points (and loop through that drawing everytime paint is raised):

GraphicsPath gp = new GraphicsPath();
Point p;
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if(!label4.Visible) label4.Visible = true;
    label4.Text = String.Format("X: {0}; Y: {1}", e.X, e.Y);
    if (panning) {
        if(p == Point.Empty) {
          p = e.Location;
          return;
        }
        gp.AddLine(p,e.Location);
        p = e.Location;
        pictureBox2.Invalidate();
    }
}
private void pictureBox2_Paint(object sender, PaintEventArgs e) {
   using(Pen p = new Pen(Color.Green,2f)){
        p.StartCap = p.EndCap = LineCap.Round;
        p.LineJoin = LineJoin.Round;
        e.Graphics.DrawPath(p,gp);
   }
}

Note that you should add using System.Drawing.Drawing2D; before using the code.