Drawing a Polygon in GDI+

In this article I will explain how to draw a Polygon in GDI+.

This article has been excerpted from book "Graphics Programming with GDI+ ".

A polygon is a closed shape with three of more straight sides. Examples of polygons include triangles and rectangles.

The Graphics class provides a DrawPolygon method to draw polygons. DrawPolygon draws a polygon defined by an array of points. It takes two arguments: a pen and an array of Points or PointF structures.

To draw a polygon, an application first creates a pen and an array of points and then calls the DrawPolygon method with these parameters. Listing 3.19 draws a polygon with five points.

LISTING 3.19: Drawing a polygon

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication11
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Paint(object sender,
        System.Windows.Forms.PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            // Create a pen
            Pen greenPen = new Pen(Color.Green, 2);
            Pen redPen = new Pen(Color.Red, 2);

            // Create points for polygon
            PointF pt1 = new PointF(40.0F, 50.0F);
            PointF pt2 = new PointF(60.0F, 70.0F);
            PointF pt3 = new PointF(80.0F, 34.0F);
            PointF pt4 = new PointF(120.0F, 180.0F);
            PointF pt5 = new PointF(200.0F, 150.0F);
            PointF[] ptsArray =
        {
              pt1, pt2, pt3, pt4, pt5
        };

            // Draw polygon
            e.Graphics.DrawPolygon(greenPen, ptsArray);

            // Dispose of object
            greenPen.Dispose();
            redPen.Dispose();
        }
    }
}

Figure 3.26 shows the output from Listing 3.19



FIGURE 3.26: Drawing a polygon

Conclusion

Hope the article would have helped you in understanding how to draw a Polygon  in GDI+. Read other articles on GDI+ on the website.

This book teaches .NET developers how to work with GDI+ as they develop applications that include graphics, or that interact with monitors or printers. It begins by explaining the difference between GDI and GDI+, and covering the basic concepts of graphics programming in Windows.