vb2010 Lesson 22

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VB2010 Lesson 22- Managing Graphics -Drawing Rectangle

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 various shapes such as rectangle, square,ellipse and circle.

22.1 Creating Rectangles

To draw a rectangle on the screen in VB2010, 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 coordinate and it 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 sample 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 sample 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

22.2 Customizing Line Style of the Pen Object

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

Where the last argument Dot specifies a particular line DashStyle value, a line that makes up of dots here. 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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VB2010 Lesson 22- Managing Graphics -Drawing Rectangle