how to mark a cross on the picture in the picture box using c#

[tty1358]

i wanted to mark a cross on the image in the picture box once i click the mouse there will be a marking like cross or dot , as i wanted to track back the time and signal at that point , i do not want to just draw . ty

[rliq]

You can handle the PictureBox's MouseDown and/or MouseUp events. The MouseEventArgs parameter holds the information you need.

Not sure what you mean by time and signal? DateTime.Now ?

PictureBox.Invalidate() will cause it to be redrawn. Do all of your drawing in the PictureBox's Paint handler.

[rliq]

This draw a circle, but you get the idea....

    public partial class Form1 : Form
    {
        List<Point> _points = new List<Point>();

        public Form1()
        {
            InitializeComponent();
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            PictureBox pb = sender as PictureBox;

            _points.Add(e.Location);
            pb.Invalidate(); // can be optimised by passing a Rectangle the same size as that used in the Paint handler 
        }

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            foreach (Point p in _points)
            {
                g.DrawEllipse(Pens.Black, new Rectangle(p.X - 5, p.Y - 5, 10, 10));
            }
        }
    }

[rliq]

For a cross (as in a plus sign) replace the Paint handler with this:

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            foreach (Point p in _points)
            {
                Point pt1 = new Point(p.X, p.Y - 10);
                Point pt2 = new Point(p.X, p.Y + 10);
                Point pt3 = new Point(p.X - 10, p.Y);
                Point pt4 = new Point(p.X + 10, p.Y);
                g.DrawLine(Pens.Black, pt1, pt2);
                g.DrawLine(Pens.Black, pt3, pt4);
            }
        }

[rliq]

You can add a Label control to display the time of the click as follows:

        List<Point> _points = new List<Point>();

        public Form1()
        {
            InitializeComponent();
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            PictureBox pb = sender as PictureBox;

            _points.Add(e.Location);
            pb.Invalidate();

            Label lbl = new Label();
            pb.Controls.Add(lbl);

            lbl.Location = new Point(e.Location.X + 4, e.Location.Y + 4);
            lbl.Text = DateTime.Now.ToLongTimeString();

        }

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            Point ptCurrent = new Point(0,0);

            foreach (Point p in _points)
            {
                Point pt1 = new Point(p.X, p.Y - 10);
                Point pt2 = new Point(p.X, p.Y + 10);
                Point pt3 = new Point(p.X - 10, p.Y);
                Point pt4 = new Point(p.X + 10, p.Y);
                g.DrawLine(Pens.Black, pt1, pt2);
                g.DrawLine(Pens.Black, pt3, pt4);

            }
        }