Drawing Other Objects with Line Caps and Styles in GDI+

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

So far we have applied line caps and line styles only to lines, but these effects can also be applied to other objects, including curves, rectangles, and ellipses. However, some of these objects impose limitations. For example, rectangles, ellipses, and closed curves do not have starting and ending caps, so the StartCap and EndCap properties of a pen will not affect them.

Let's add one more menu item to MainMenu, called OtherObjects. The code for its menu item click event handler is given in Listing 9.5. We create three pens with different colors and widths; set their line cap, dash style, and dash cap properties; and draw a rectangle, an ellipse, and a curve.

LISTING 9.5: Drawing other objects using line caps, dash styles, and dash caps

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Drawing.Drawing2D;

using System.Windows.Forms;

namespace DrawingOtherObjectsLine

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void Form1_Paint(object sender, PaintEventArgs e)

        {

            Graphics g = this.CreateGraphics();

            g.Clear(this.BackColor);

            g.SmoothingMode = SmoothingMode.AntiAlias;

            // Create pen objects

            Pen blackPen = new Pen(Color.Black, 5);

            Pen bluePen = new Pen(Color.Blue, 8);

            Pen redPen = new Pen(Color.Red, 4);

            // Set DashCap styles

            blackPen.StartCap = LineCap.DiamondAnchor;

            blackPen.EndCap = LineCap.SquareAnchor;

            blackPen.DashStyle = DashStyle.DashDotDot;

            blackPen.DashPattern = new float[] { 10 };

            blackPen.DashCap = DashCap.Triangle;

            // Set blue pen dash style and dash cap

            bluePen.DashStyle = DashStyle.DashDotDot;

            bluePen.DashCap = DashCap.Round;

            // Set red pen line cap and line dash styles

            redPen.StartCap = LineCap.Round;

            redPen.EndCap = LineCap.DiamondAnchor;

            redPen.DashCap = DashCap.Triangle;

            redPen.DashStyle = DashStyle.DashDot;

            redPen.DashOffset = 3.4f;

            // Draw a rectangle

            g.DrawRectangle(blackPen, 20, 20, 200, 100);

            // Draw an ellipse

            g.DrawEllipse(bluePen, 20, 150, 200, 100);

            // Draw a curve

            PointF pt1 = new PointF(90.0F, 40.0F);

            PointF pt2 = new PointF(130.0F, 80.0F);

            PointF pt3 = new PointF(200.0F, 100.0F);

            PointF pt4 = new PointF(220.0F, 120.0F);

            PointF pt5 = new PointF(250.0F, 250.0F);

            PointF[] ptsArray =

            {

            pt1, pt2, pt3, pt4, pt5

            };

            g.DrawCurve(redPen, ptsArray);

            // Dispose of objects

            blackPen.Dispose();

        }

    }

}

Figure 9.7 shows the output from Listing 9.5. Each graphics object rectangle, ellipse, and curve has a different style.

FIGURE 9.7: A rectangle, an ellipse, and a curve with different line styles

Conclusion

Hope the article would have helped you in understanding image class methods and properties 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.