how to find the coordinate points of polygon?

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in my code i am trying to draw polygon i need to find coordinate points of polygon and display that coordinate points in to text Boxes .can anybody help me to figure it out ...

C#

List<point> points = new List<point>();
         private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
       {
           //points.Clear();
           // points.Push(e.Location);

           if (e.Button == MouseButtons.Left)
           {
               points.Add(e.Location);

               pictureBox1.Invalidate();
           }


          private void pictureBox1_Paint(object sender, PaintEventArgs e)
            {
           if (points.Count > 1)
               e.Graphics.DrawPolygon(Pens.DarkBlue, points.ToArray());

           foreach (Point p in points)
           {
               e.Graphics.FillEllipse(Brushes.Red,
                                      new Rectangle(p.X - 2, p.Y - 2, 4, 4));
           }
           }</point></point>

Posted 2-May-14 20:57pm

Member 10785117

Updated 2-May-14 22:14pm

Sampath Lokuge

v2

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Mitchell J. 3-May-14 3:25am

What have you tried yourself that isn't working? Is there anything you might have tried already but haven't because you did't think it would work?

I'm asking this because the solution, if I gave it to you, would actually be really, really simple...

Member 10785117 3-May-14 3:49am

with above code i am drawing polygon on mouse click with highlighting the coordinate points but i don't know how to get coordinate points with respect to picture box if you have any answer please help me

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OriginalGriff · Accepted Answer · 2014-05-02T22:04:00

Solution 1

You have your coordinates already: they are in the points collection.
So all you need to do is convert each Point to a string, and display it - but I wouldn't use TextBoxes, because there are a variable number of Points, depending on how many times the user clicks - and if each one needs a textbox... yuck.

A better solution is to use a single multiline textbox, or a datagridview. The later is simple:

C#

myDdataGridView.DataSource = null;
myDataGridView.DataSource = points;

The system will sort out the display for you. (You need the first line to "refresh" the DataGridView)

Posted 2-May-14 22:04pm

OriginalGriff

Comments

Member 10785117 3-May-14 4:28am

on mouse click i am getting coordinates points in to datagrid view twice for a single click ...

OriginalGriff 3-May-14 4:39am

Strange: I just tried with your code and it worked fine: red dots, connected by black lines, and one point per click.
List<Point> points = new List<Point>();
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
points.Add(e.Location);

pictureBox1.Invalidate();
dataGridView1.DataSource = null;
dataGridView1.DataSource = points;
}
}

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
if (points.Count > 1)
e.Graphics.DrawPolygon(Pens.DarkBlue, points.ToArray());

foreach (Point p in points)
{
e.Graphics.FillEllipse(Brushes.Red,
new Rectangle(p.X - 2, p.Y - 2, 4, 4));
}
}
So...Have you checked that there is nowhere else you add items to the Points list?

Member 10785117 3-May-14 5:28am

ya i checked out with what you wrote here ,but i am getting coordinates point twice in a single click in datagridview ..how can i resolve it ?<br>

OriginalGriff 3-May-14 5:53am

Do you mean you get an X and a Y in separate columns in the view?
Or that you get x=2, y=5 repeated?

Member 10785117 3-May-14 5:57am

x=2,y=5 these coordinates are repeated twice in two rows....on every click i am getting twice

OriginalGriff 3-May-14 6:33am

So - right click on the points collection in your code, and select "Find All References"
Look at the results list: How many times do you have "Add" in there?

Member 10785117 3-May-14 6:54am

one time

OriginalGriff 3-May-14 7:00am

OK, do the same with pictureBox1_MouseDown
Should be just two references - the declaration, and the single time it's hooked up in the designer file.

Member 10785117 3-May-14 7:12am

OK thank you so much . how to erase content of picture box on mouse click event..is that just invalidating the picture box in button mouse click event?

OriginalGriff 3-May-14 7:20am

Yes - if you empty the points collection.
The drawing it not "permanent" - it's only drawn on the screen, not on the image that the picture box is displaying.

OriginalGriff 3-May-14 8:24am

"is not working" is not very helpful - what is it doing that you didn't expect or not doing that your did? :laugh:

Member 10785117 3-May-14 8:04am

Thank you.

Mitchell J. · Accepted Answer · 2014-05-02T22:10:00

The solution is so simple because you have practically written the solution in that code snippet already, unless I am missing something that you haven't explained.

Here, where you did this:

C#

foreach (Point p in points)
{
   e.Graphics.FillEllipse(Brushes.Red,
   new Rectangle(p.X - 2, p.Y - 2, 4, 4));
}

Can't you just create a function called UpdateTextbox(), like this?

C#

void UpdateTextbox()
{
   exampletextbox.Text = ""; 
   foreach (Point p in points)
   {
      exampletextbox.Text += p.ToString();
   }
}

You can customize the way that you represent the coodinates, but really this code is not that different from what you have already. points is defined globally, so you can use it in this function. All you need to do is call UpdateTextbox() at an appropriate moment, say in pictureBox1_MouseDown.