Learning Java

Displaying Images

So far, we’ve worked with methods for drawing simple shapes and displaying text. For more complex graphics, we’ll be working with images. The 2D API has a powerful set of tools for generating and displaying image data. These tools address the problems of working in a distributed and multithreaded application environment. We’ll start with the basics of the java.awt.Image class and see how to get an image into an applet or application and draw it on a display. This job isn’t quite as simple as it sounds; the browser might have to retrieve the image from a networked source when we ask for it. Fortunately, if we’re just interested in getting the image on the screen whenever it’s ready, we can let the graphics system handle the details for us. In the next chapter, we’ll discuss how to manage image loading manually, as well as how to create raw image data and feed it efficiently to the rest of an application.

The Image Class

The java.awt.Image class represents a view of an image. The view is created from an image source that produces pixel data. Images can be from a static source, such a GIF, JPEG, or PNG data file, or a dynamic one, such as a video stream or a graphics engine. The Image class in Java 2 also handles GIF89a animations, so that you can work with simple animations as easily as static images.

An applet can ask its viewer to retrieve an image by calling the getImage( ) method. The location of the image to be retrieved is given as a URL, either absolute ...