Image class methods and properties in GDI+

This article has been excerpted from book "Graphics Programming with GDI+".

Before we write any imaging code, let's explore the .NET Framework library and see what kind of imaging support it offers. The Bitmap class provides functionality to work with raster images, and the Metafile class provides functionality to work with vector images. Both classes are inherited from the Image class. In this article we will discuss the Image and Bitmap classes and their members.

We'll start this discussion with the Image class, which is defined in the System.Drawing namespace. Understanding this class is important because we will be using its members in our samples throughout this article.

The Image class is an abstract base class for the Bitmap, Metafile, and Icon classes. Some common Image class properties (all read-only) are described in Table 7.2.

The Pixel Format

The pixel format (also known as color depth) defines the number of bits within each pixel. The format also defines the order of color components within a single pixel of data. In the .NET Framework library, the PixelFormat enumeration represents the pixel format.

Beside the properties discussed in Table 7.2, the Image class provides methods, which are described in Table 7.3.

An Image Viewer Application

Now we will write an application that will use some of the properties and methods of the Image class. You will learn to open, view, manipulate, and save images. The application is a simple image viewer.

TABLE 7.2: Image class properties

To begin:

1. Use Visual Studio .NET to create a Windows application project called ImageViewer.
2. Add a MainMenu control and some menu item to the form.
3. Change the text of the menu items to File, Open File, Save File and Exit, and the name of these menu items to FileMenu, OpenFileMenu, SaveFileMenu, and ExitMenu, respectively. The final form looks like Figure 7.3.
4. Write menu click event handlers for the OpenFileMenu, SaveFileMenu, and ExitMenu items by simply double-clicking on them.

The OpenFileMenu click event handler will allow us to browse and select one image and display it, the SaveFileMenu click event handler will save the image as a new file name, and the ExitMenu click event handler will simply close the application.

Before we write code for these menu event handlers, let's see how to create an Image object from a file and how to display it using the DrawImage method of the Graphics class.

TABLE 7.3: Image class methods

FIGURE 7.3: A simple image viewer application

Conclusion

Hope the article would have helped you in understanding image class methods and properties in GDI+. Read other articles on GDI+ on the website.

This book teaches .NET developers how to work with GDI+ as they develop applications that include graphics, or that interact with monitors or printers. It begins by explaining the difference between GDI and GDI+, and covering the basic concepts of graphics programming in Windows.