Visual Basic.NET How to Program (PDF)

Chapter 16 Graphics and Multimedia 705
Lines 30–32 perform similar functions, except that the specified arc sweeps -270
degrees. The Size property of a Rectangle determines the arc’s height and width. Line
36 sets the Size property to a new Size object, which changes the size of the rectangle.
The remainder of the program is similar to the portions described above, except that a
SolidBrush is used with method FillPie. The resulting arcs, which are filled, can be
seen in the bottom half of the screenshot Fig. 16.18.
16.7 Drawing Polygons and Polylines
Polygons are multisided shapes. There are several Graphics methods used to draw polygons:
DrawLines draws a series of connected points, DrawPolygon draws a closed
polygon and FillPolygon draws a solid polygon. These methods are described in
Fig. 16.19. The program in Fig. 16.20 allows users to draw polygons and connected lines
via the methods listed in Fig. 16.19.
Method Description
DrawLines Draws a series of connected lines. The coordinates of each point are specified
in an array of Points. If the last point is different from the first point,
the figure is not closed.
DrawPolygon Draws a polygon. The coordinates of each point are specified in an array of
Point objects. This method draws a closed polygon, even if the last point
is different from the first point.
FillPolygon Draws a solid polygon. The coordinates of each point are specified in an
array of Points. This method draws a closed polygon, even if the last
point is different from the first point.
Fig. 16.19 Graphics methods for drawing polygons.
1 ' Fig. 16.20: DrawPolygons.vb
2 ' Demonstrating polygons.
3
4 Public Class FrmPolygon
5 Inherits System.Windows.Forms.Form
6
7 ' polygon type options
8 Friend WithEvents filledPolygonRadio As RadioButton
9 Friend WithEvents lineRadio As RadioButton
10 Friend WithEvents polygonRadio As RadioButton
11
12 ' command buttons
13 Friend WithEvents cmdClear As Button
14 Friend WithEvents cmdNewColor As Button
15
16 Friend WithEvents drawWindow As Panel
17 Friend WithEvents typeGroup As GroupBox
Fig. 16.20 Polygon drawing demonstration (part 1 of 4).