Drawing Polygon & Pie

A polygon is a closed plane figure bounded by three or more straight sides. To draw a polygon on the screen, you must define all the points, also called vertices, that join together to form the shape. :contentReference[oaicite:1]{index=1}

The syntax to define the points of a polygon is:

Dim A1 As New Point(X1, Y1)
Dim A2 As New Point(X2, Y2)
Dim A3 As New Point(X3, Y3)
Dim A4 As New Point(X4, Y4)
...
Dim An As New Point(Xn, Yn)

After declaring the points, you group them together in a point structure like this:

Dim myPoints As Point() = {A1, A2, A3, ..., An}

Finally, create the Graphics object and use the DrawPolygon method:

Dim myGraphics As Graphics = Me.CreateGraphics()
myGraphics.DrawPolygon(myPen, myPoints)

where myPen is the Pen object, for example:

myPen = New Pen(Drawing.Color.Blue, 5)

A triangle is a polygon with three vertices. The code is:

Private Sub BtnDraw_Click(sender As Object, e As EventArgs) Handles BtnDraw.Click

    Dim myPen As Pen
    Dim A As New Point(10, 10)
    Dim B As New Point(100, 50)
    Dim C As New Point(60, 150)
    Dim myPoints As Point() = {A, B, C}

    myPen = New Pen(Drawing.Color.Blue, 5)

    Dim myGraphics As Graphics = Me.CreateGraphics()
    myGraphics.DrawPolygon(myPen, myPoints)

End Sub

Running the program produces the image shown below.

A quadrilateral is a polygon with four sides, so you need four vertices.

Private Sub BtnDraw_Click(sender As Object, e As EventArgs) Handles BtnDraw.Click

    Dim myPen As Pen
    Dim A As New Point(10, 10)
    Dim B As New Point(100, 50)
    Dim C As New Point(120, 150)
    Dim D As New Point(60, 200)
    Dim myPoints As Point() = {A, B, C, D}

    myPen = New Pen(Drawing.Color.Blue, 5)

    Dim myGraphics As Graphics = Me.CreateGraphics()
    myGraphics.DrawPolygon(myPen, myPoints)

End Sub

The output image is shown below.

To draw a pie, use the DrawPie method of the Graphics object. As usual, you must first create the Graphics and Pen objects. The syntax is:

myGraphics.DrawPie(myPen, X, Y, width, height, StartAngle, SweepAngle)

Where:

• X, Y are the coordinates of the bounding rectangle
• width and height determine the size of the pie
• StartAngle is the starting angle in degrees
• SweepAngle is the angle through which the arc is drawn

Both angles are measured in degrees. If the sweep angle is positive, it moves clockwise. If it is negative, it moves anticlockwise. :contentReference[oaicite:2]{index=2}

The following example draws a pie that starts at 0 degrees and sweeps clockwise through 60 degrees.

Private Sub BtnDraw_Click(sender As Object, e As EventArgs) Handles BtnDraw.Click

    Dim myPen As Pen
    myPen = New Pen(Drawing.Color.Blue, 5)

    Dim myGraphics As Graphics = Me.CreateGraphics()
    myGraphics.DrawPie(myPen, 50, 50, 150, 150, 0, 60)

End Sub

The output image is shown below.