The Graphics Class

The Graphics class is center of all GDI+ classes. After discussing graphics class, I'll discuss some common GDI+ objects and their representation and then we'll see some sample applications to apply this theory in our applications and how it works.

The Graphics class plays a vital role in GDI+. No matter where you go, you go through this class ;). The Graphics class encapsulates GDI+ drawing surfaces. Before drawing any object (for example circle, or rectangle ) we have to create a surface using Graphics class.

There're different of ways to get a graphics object in your application. You can either get a graphics object on your form's paint event or by overriding OnPaint() method of a form. These both have one argument of type System.Windows.Forms.PaintEventArgs. You call its Graphics member to get the graphics object in your application. For example:

protected overrides sub OnPaint(ByVal e As 
                          System.Windows.Forms.PaintEventArgs)
      Dim g As Graphics = e.Graphics
End Sub 

Now you've the Graphics object. Now you can do any thing you want. The Graphics class has tons of methods to drawing graphics objects such as fonts, pens, lines, path and polygons, images and ellipse and so on. Some of the graphics class members are described in the following table -

DrawArc	This method draws an arc.
DrawBezier, DrawBeziers, DrawCurve	These methods draw a simple and bazier curves. These curvers can be closed, cubic and so on.
DrawEllipse	Draws an ellipse or circle.
DrawImage	Draws an image.
DrawLine	Draws a line.
DrawPath	Draws the path (lines with GraphicsPath )
DrawPie	Draws the outline of a pie section.
DrawPolygon	Draws the outline of a polygon.
DrawRectangle	Draws the outline of a rectangle.
DrawString	Draws a string.
FillEllipse	Fills the interior of an ellipse defined by a bounding rectangle.
FillPath	Fills the interior of a path.
FillPie	Fills the interior of a pie section.
FillPolygon	Fills the interior of a polygon defined by an array of points.
FillRectangle	Fills the interior of a rectangle with a Brush
FillRectangles	Fills the interiors of a series of rectangles with a Brush
FillRegion	Fills the interior of a Region.

Now say, if you want to draw an ellipse using the same method we've described above, you override OnPaint method and write the following code -

protected overrides sub OnPaint(ByVal e As 
                              System.Windows.Forms.PaintEventArgs)

Dim g As Graphics = e.Graphics
  Dim pn As Pen = New Pen(Color.Green, 10)
  g.DrawLine(pn, 100, 10, 30, 10)
  g.DrawEllipse(New Pen(Color.Red, 20), 20, 40, 20, 20)
  End Sub

That will draw a ellipse. Before we see more samples, let's discuss some GDI+ objects.

GDI+ Font, Brush and Bitmap

GDI+ GraphicsPath and LinearGradientBrush

GDI+ Printing.

GDI+ and DrawArc and DrawPath

GDI+ Color and ARGB with Example