This article has been
excerpted from book "Graphics Programming with GDI+".
In this article we will create a pen, set its line cap and line dash styles, and
use it- but this time, drawing graphics shapes, rather than simple lines.
Listing 4.21 creates several pens and uses them to draw an arc, Brezier curve,
rectangle, and ellipse with the help of the DrawArc, DrawBezier, DrawRectangle,
and DrawEllipse methods of the Graphics class.
LISTING 4.21: Using different pens to draw various graphics objects
using System;
using
System.Collections.Generic;
using
System.ComponentModel;
using System.Data;
using
System.Drawing;
using
System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using
System.Windows.Forms;
namespace
WindowsFormsApplication4
{
public partial
class Form1 :
Form
{
public Form1()
{
InitializeComponent();
}
private void
Form1_Paint(object sender,
PaintEventArgs e)
{
Graphics g =
this.CreateGraphics();
g.Clear(this.BackColor);
Pen redPen =
new Pen(new
SolidBrush(Color.Red),
4);
Pen bluePen =
new Pen(new
SolidBrush(Color.Blue),
5);
Pen blackPen =
new Pen(new
SolidBrush(Color.Black),
3);
//Set line styles
redPen.DashStyle = DashStyle.Dash;
redPen.SetLineCap(LineCap.DiamondAnchor,
LineCap.ArrowAnchor, DashCap.Flat);
bluePen.DashStyle = DashStyle.DashDotDot;
bluePen.StartCap = LineCap.Triangle;
bluePen.EndCap = LineCap.Triangle;
bluePen.DashCap = DashCap.Triangle;
blackPen.DashStyle = DashStyle.Dot;
blackPen.DashOffset = 3.4F;
blackPen.SetLineCap(LineCap.RoundAnchor,
LineCap.Square, DashCap.Round);
//Draw objects
g.DrawArc(redPen, 10.0F, 10.0F, 50, 100, 45.0F, 90.0F);
g.DrawRectangle(bluePen, 60, 80, 140, 50);
g.DrawBezier(blackPen, 20.0F, 30.0F, 100.0F, 200.0F, 40.0F, 400.0F,
100.0F, 200.0F);
g.DrawEllipse(redPen, 50, 50, 200, 100);
//Dispose of objects
redPen.Dispose();
bluePen.Dispose();
blackPen.Dispose();
g.Dispose();
}
}
}
Figure 4.26 shows the output of Listing 4.21. All of the elements drawn have
line cap and dash styles.
Transformation with Pens
Transformation is the process of changing graphics objects from one state to
another. Rotation, scaling, reflection, translation, and shearing are examples
to transform.
FIGURE 4.26: Graphics shapes with cap and dash styles
The Pen class provides methods for transformation and rotation. The
RotateTransform method rotates a transformation by an angle. This method takes a
rotation angle of type float. The second argument, MatrixOrder, is an optional
parameter that provides an order for matrix transformation operations. The
MatrixOrder enumeration defines the matrix order, which has two members: Append
and Prepend. The matrix order is the order in which a matrix is multiplied with
other matrices.
The difference between Append and Prepend is the order of the operation. For
example, if two operations are participating in a process, the second operation
will be performed after the first when the matrix order is Append; when the
order is Prepend, the second operation will be performed before the first.
The MultiplyTransofrm method multiplies a transformation matrix by pen. Its
first argument is a Matrix object, and the optional second argument is the
matrix order of types MatrixOrder enumeration.
The TranslateTransform method of the Pen class translates a transformation by
the specified dimension. This method takes two float type values for translation
in x and y, and an optional third parameter of type MatrixOrder.
Listing 4.22 uses the ScaleTransofrm and RotateTransform methods to apply
rotation on pens and rectangles.
LISTING 4.22: Applying transformation on pens
using System;
using
System.Collections.Generic;
using
System.ComponentModel;
using System.Data;
using
System.Drawing;
using
System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using
System.Windows.Forms;
namespace
WindowsFormsApplication4
{
public partial
class Form1 :
Form
{
public Form1()
{
InitializeComponent();
}
private void
Form1_Paint(object sender,
PaintEventArgs e)
{
Graphics g =
this.CreateGraphics();
g.Clear(this.BackColor);
//Create a Pen Object
Pen bluePen =
new Pen(Color.Blue,
10);
Pen redPen =
new Pen(Color.Red,
5);
//Supply rotate and scale transformations
bluePen.ScaleTransform(3, 1);
g.DrawEllipse(bluePen, 20, 20, 100, 50);
g.DrawRectangle(redPen, 20, 120, 100, 50);
bluePen.RotateTransform(90, MatrixOrder.Append);
redPen.ScaleTransform(4, 2, MatrixOrder.Append);
g.DrawEllipse(bluePen, 220, 20, 100, 50);
g.DrawRectangle(redPen, 220, 120, 100, 50);
//Dispose of objects
redPen.Dispose();
bluePen.Dispose();
g.Dispose();
}
}
}
Figure 4.27 shows the output from Listing 4.22. The first ellipse and rectangle
are drawn normally. The second ellipse and rectangle are drawn after rotation
and scaling have been applied to their pens.
FIGURE 4.27: Rotation and scaling
Note: You need to reference the System.Drawing.Drawing2D namespace in
order to run the code in the listings of this section because the Matrix class
and the MatrixOrder enumeration are defined in this namespace.
Conclusion
Hope the article would have helped you in understanding Drawing Other Graphics
Shapes by Applying Cap and Dashed Line Styles in GDI+. Read other articles on GDI+ on the website.
![bookGDI.jpg]()
|
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. |