We have learned how to create the Graphics and the Pen objects to draw straight lines in the previous lesson. Now we shall learn how to draw rectangle, square,ellipse and circle.
To draw a rectangle on the screen in VB2008, there are two ways: (i)The first way is to draw a rectangle directly using the DrawRectangle method by specifying its upper-left corner's coordinates and its width and height. You also need to create a Graphics and a Pen object to handle the actual drawing. The method to draw the rectangle is DrawRectangle .
The syntax is:
myGrapphics.DrawRectangle(myPen, X, Y, width, height)
Where myGraphics is the variable name of the Graphics object and myPen is the variable name of the Pen object created by you. You can use any valid and meaningful variable names. X, Y is the coordinate of the upper left corner of the rectangle while width and height are self-explanatory, i.e, the width and height of the rectangle. The code is shown below:
Dim myPen As Pen
myPen = New Pen(Drawing.Color.Blue, 5)
Dim myGraphics As Graphics = Me.CreateGraphics
myGraphics.DrawRectangle(myPen, 0, 0, 100, 50)
(ii) The second way is to create a rectangle object first and then draw this triangle using the DrawRectangle method. The syntax is as shown below:
myGraphics.DrawRectangle(myPen,myRectangle)
where myRectangle is the rectangle object created by you, the user.
The code to create a rectangtle object is as shown below:
Dim myRectangle As New Rectangle
myRect.X = 10 myRect.Y = 10
myRect.Width = 100
myRect.Height = 50
You can also create a rectangle object using a one-line code as follows:
Dim myRectangle As New Rectangle(X,Y,width, height)
and the code to draw the above rectange is
myGraphics.DrawRectangle(myPen, myRectangle)
The full code is shown below:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim myRect As New Rectangle
myRect.X = 10
myRect.Y = 10
myRect.Width = 100
myRect.Height = 50
Dim myPen As Pen
myPen = New Pen(Drawing.Color.Blue, 5)
Dim myGraphics As Graphics = Me.CreateGraphics
myGraphics.DrawRectangle(myPen, myRect)
End Sub
The shape we draw so far are drawn with solid line, we can actually customize the line style of the Pen object so that we have dotted line, line consisting of dashes and more. For example, the syntax to draw with dotted line is shown below:
myPen.DashStyle=Drawing.Drawing2D.DashStyle.Dot
The last argument ,Dot , specifies a particular line DashStyle value, a line that makes up of dots . The following code draws a rectangle with red dotted line.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim myPen As Pen
myPen = New Pen(Drawing.Color.Red, 5)
Dim myGraphics As Graphics = Me.CreateGraphics
myPen.DashStyle = Drawing.Drawing2D.DashStyle.Dot
myGraphics.DrawRectangle(myPen, 10, 10, 100, 50)
End Sub
The output image is shown below:
The possible values of the line DashStyle of the Pen are listed in the table below:
| DashStyle Value | Line Style |
|---|---|
| Dot | Line consists of dots |
| Dash | Line consists of dashes |
| DashDot | Line consists of alternating dashes and dots |
| DashDotDot | Line consists of alternating dashes and double dots |
| Solid | Solid line |
| Custom | Custom line style |
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