Visual Basic.NET How to Program (PDF)

714 Graphics and Multimedia Chapter 16
16.9 Introduction to Multimedia
Visual Basic offers many convenient ways to include images and animations in programs.
People who entered the computing field decades ago used computers primarily to perform
arithmetic calculations. As the discipline evolves, we are beginning to realize the importance
of computers’ data-manipulation capabilities. We are seeing a wide variety of exciting
new three-dimensional applications. Multimedia programming is an entertaining and
innovative field, but one that presents many challenges
Multimedia applications demand extraordinary computing power. Until recently,
affordable computers with this amount of power were not available. However, today’s
ultrafast processors are making multimedia-based applications commonplace. As the
market for multimedia explodes, users are purchasing faster processors, larger memories
and wider communications bandwidths needed to support multimedia applications. This
benefits the computer and communications industries, which provide the hardware, software
and services fueling the multimedia revolution.
In the remaining sections of this chapter, we introduce the use and manipulation of
images, as well as other multimedia features and capabilities. Section 16.10 discusses how
to load, display and scale images; Section 16.11 demonstrates image animation;
Section 16.12 presents the video capabilities of the Windows Media Player control; and
Section 16.13 explores Microsoft Agent technology.
16.10 Loading, Displaying and Scaling Images
Visual Basic’s multimedia capabilities include graphics, images, animations and video.
Previous sections demonstrated Visual Basic’s vector-graphics capabilities; this section
concentrates on image manipulation. The Windows form that we create in Fig. 16.23 demonstrates
the loading of an Image (System.Drawing namespace). The application allows
users to enter a desired height and width for the Image, which then is displayed in
the specified size.
1 ' Fig. 16.23: DisplayLogo.vb
2 ' Displaying and resizing an image.
3
4 Public Class FrmDisplayLogo
5 Inherits System.Windows.Forms.Form
6
7 ' width controls
8 Friend WithEvents txtWidth As TextBox
9 Friend WithEvents lblWidth As Label
10
11 ' height controls
12 Friend WithEvents lblHeight As Label
13 Friend WithEvents txtHeight As TextBox
14
15 Private mGraphicsObject As Graphics
16 Private mImage As Image
17
Fig. 16.23 Image resizing (part 1 of 3).