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Summary
GDI+ is an improved version of Microsoft's graphics device interface (GDI) API. In this chapter we learned how GDI+ is designed for use in both managed and unmanaged code.
System.Drawing
and its helper namespaces defined in the .NET Framework library provide a managed class wrapper to write managed GDI+ applications. We also learned the basics and definition of GDI+ and what major improvements are
Now that you've learned the basics of GDI+, the
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Chapter 2. Your First GDI+ Application
In this chapter we move to the more practical aspects of writing graphics applications using GDI+ in the .NET Framework. This chapter is the foundation chapter and discusses
To write a graphics application, a good understanding of drawing surfaces and coordinate systems is necessary. We will begin by discussing these concepts and how they are represented in GDI+. Then you'll learn step-by-step how to write a graphics application in the .NET Framework using GDI+. We will cover the following topics:
At the end of this chapter we will discuss some basic graphics structures and their
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2.1 Drawing Surfaces
Every drawing application (regardless of the operating system), consists of three common
To draw graphics objects you need to have a pen or a brush, which defines the texture, color, and width of the drawing. For example, if you draw a line or a rectangle, you need to create a pen with a color and width. The process component of the drawing application includes making a call to draw the line or rectangle on the form. Each drawing surface has four common properties: width, height, resolution, and color depth.
Definition: Pixel A pixel is the smallest element that participates in the drawing process to display graphics objects or images on the screen. The pixel density is often represented by a value in dots per inch (dpi).
The quality of a pixel is directly proportional to the color depth. The
Color
structure represents a color in GDI+. It has four components: alpha, red, green, and blue. The
RGB
(
red-green-blue
)
components
of a color represent the number of possible colors (see Figure 2.1). Each component in RGB has 256 (2
8
) color combinations. Hence all three components of GDI+ color represent 256x256x256 possible colors. The
alpha component
determines the transparency of the color, which affects how the color
Figure 2.1. Color components in GDI+
To see the proper colors defined in the GDI+ color structure, a drawing surface must support at least a 24-bit color system (for the RGB components of a color structure), which means that each pixel of the surface must be able to hold 24 bits (8 bits each for the R, G, and B components, as noted already). Surfaces with less than 24 bits per pixel may not display graphics objects and images exactly as defined in a drawing application. We will discuss colors in more detail in Chapter 5.
Note The color depth of a surface is different from the color depth of a particular display device, such as a monitor or a printer. Most monitors can support over a million colors, and some printers may support only black and white. GDI+ provides three types of drawing surfaces: forms, printers, and bitmaps. 2.1.1 Forms as a SurfaceWhen you write a Windows application that draws something on a form, the form acts as a drawing surface and supports all the properties required by a drawing surface. 2.1.2 Printers as a Surface
When you print from an application, the printer acts as a drawing surface. You can set a printer's resolution and color depth, as well as the height and width of the paper. We will discuss printer-
2.1.3 Bitmaps as a SurfaceWhen you create images in memory and save them as a bitmap, the bitmap functions as a drawing surface. You can set the image width, height, resolution, and color depth properties. Bitmap surfaces are commonly used for writing graphics Web applications. Drawing works a little differently in Web applications. For example, if you want to draw a line and a rectangle in a Web page using GDI+, you need to create an image, use this image as a surface for the line and rectangle objects, set its surface-related properties, and then send the image to the browser. We will discuss Web graphics applications in more detail in Chapter 12. |
