This article has been
excerpted from book "Graphics Programming with GDI+".
The alignment of a pen represents its position respective to a line. The
PenAlignment enumeration specifies the alignment of a pen-meaning the center
point of the pen width relative to the line. Table 4.11 describes the members of
the PenAlignment enumeration.
To see alignment in action, let's create a sample application. We create a
Windows application, and add a combo box, three labels, two buttons, and a
numeric up-down control. We change the control properties, and the final form
looks like Figure 4.21.
FIGURE 4.21: Our pen alignment application
TABLE 4.11: PenAlignment members
|
Member |
Description |
|
Center |
The pen is
centered. |
|
Inset |
The pen is inside
the line. |
|
Left |
The pen is left of
the line. |
|
Outset |
The pen is outside
of the line. |
|
Right |
The pen is right
of the line. |
The Pen Alignment combo box lists the alignment of a pen. Pen Width represents
the width of the pen, and Pen Color lets you pick the color of the pen. The Pen
Color button click event handler simply sets the color of the pen and stores the
selected color in a Color type variable at the class level, as shown in Listing
4.17.
LISTING 4.17: The Pen Color button click event handler
private Color
penColor = Color.Red;
private void
ColorBtn_Click(object sender, System.EventArgs
e)
{
//Use ColorDialog to select a color
ColorDialog clrDlg =
new ColorDialog();
if (clrDlg.ShowDialog() ==
DialogResult.OK)
{
//Save color as background color
//and fill text box with this color
penColor =
clrDlg.Color;
ColorBtn.BackColor = penColor;
}
}
Listing 4.18 (on the form's load event handler) loads all alignments to the
combo box.
LISTING 4.18: Adding pen alignments to the combo box
private
void Form1_Load(object
sender, System.EventArgs e)
{
AddPenAlignments();
}
private void
AddPenAlignments()
{
//Add pen alignment
comboBox1.Items.Add(PenAlignment.Center);
comboBox1.Text
=
PenAlignment.Center.ToString();
comboBox1.Items.Add(PenAlignment.Inset);
comboBox1.Items.Add(PenAlignment.Left);
comboBox1.Items.Add(PenAlignment.Outset);
comboBox1.Items.Add(PenAlignment.Right);
}
Finally, in Listing 4.19 we write code for the Draw Graphics button click event
handler. We set the Width and Color properties of the pen after reading values
from the form's controls. Then we look for the current alignment set by the user
in the combo box and set the Alignment property of the pen. In the end, we use
this pen to draw a rectangle. We also fill one more rectangle with a linear
gradient brush.
LISTING 4.19: Creating a pen with alignment
private
void DrawBtn_Click(object
sender, System.EventArgs e)
{
//Create a Graphics object and set it clear
Graphics g = this.CreateGraphics();
g.Clear(this.BackColor);
//Create
a solid brush and a hatch brush
Pen pn1 = new
Pen(Color.Blue,
3);
pn1.Width = (float)numericUpDown1.Value;
pn1.Color =
ColorBtn.BackColor;
//Find out current pen alignment
string str = comboBox1.Text;
switch (str)
{
case "Center":
pn1.Alignment = PenAlignment.Center;
break;
case "Inset":
pn1.Alignment = PenAlignment.Inset;
break;
case "Left":
pn1.Alignment = PenAlignment.Left;
break;
case "Outset":
pn1.Alignment = PenAlignment.Outset;
break;
case "Right":
pn1.Alignment = PenAlignment.Right;
break;
default:
break;
}
//Create a pen from a hatch brush
//Draw a rectangle
g.DrawRectangle(pn1, 80, 150, 150, 150);
//Create a brush
LinearGradientBrush brush =
new LinearGradientBrush(
new Rectangle(10,
10, 20, 20), Color.Blue,
Color.Green, 45.0F);
g.FillRectangle(brush, 90, 160, 130, 130);
//Dispose of objects
pn1.Dispose();
g.Dispose();
}
Figure 4.22 shows the output from Listing 4.19. The pen width is 10 and
alignment is center.
If we set the alignment as inset, we get Figure 4.23.
FIGURE 4.22: Drawing with center pen alignment
FIGURE 4.23: Drawing with inset pen alignment
Conclusion
Hope the article would have helped you in understanding Pen Alignment 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. |