This article has been excerpted from book "Graphics Programming with GDI+ ".
FIGURE 3.5: An ellipse
Drawing Ellipses and Circles
An ellipse is a circular boundary within a rectangle, where each opposite point has the same distance from a fixed point, called the center of the ellipse. An ellipse within a square is called a circle. Figure 3.5 shows an ellipse with its height, width, and center indicated.
To draw an ellipse, you need to specify the outer rectangle. GDI+ takes care of the rest. DrawEllipse draws an ellipse defined by a rectangle specified by a pair of coordinates, a height, and a width (an ellipse with equal height and width is a circle). DrawEllipse has four overloaded methods.
public void DrawEllipse(Pen, Rectangle);
public void DrawEllipse(Pen, RectangleF);
public void DrawEllipse(Pen, int, int, int, int);
public void DrawEllipse(Pen, float, float, float, float);
To draw an ellipse, an application creates a pen and four coordinates (or a rectangle), and then calls DrawEllipse. Listing 3.5 draws ellipses with different options.
LISTING 3.5: Drawing ellipses
private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
// Create Pens
Pen redPen = new Pen(Color.Red, 6);
Pen bluePen = new Pen(Color.Blue, 4);
Pen greenPen = new Pen(Color.Green, 2);
// Create a rectangle
Rectangle rect = new Rectangle(80, 80, 50, 50);
// Draw ellipses
e.Graphics.DrawEllipse(greenPen, 100.0F, 100.0F, 10.0F, 10.0F);
e.Graphics.DrawEllipse(redPen, rect);
e.Graphics.DrawEllipse(bluePen, 60, 60, 90, 90);
e.Graphics.DrawEllipse(greenPen, 40.0F, 40.0F, 130.0F, 130.0F);
//Dispose of objects
redPen.Dispose();
greenPen.Dispose();
bluePen.Dispose();
}
Figure 3.6 shows the output from Listing 3.5
FIGURE 3.6: Drawing ellipse
Conclusion
Hope the article would have helped you in understanding drawing Ellipses and Circles in GDI+. Read other articles on GDI+ on the website.
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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. |