Java 2D Graphics

9.4. Drawing on Images

Up until now, I've treated an image as something that gets rendered on a drawing surface. But the image itself can be a drawing surface. The Image class provides the following method for this purpose:

public abstract Graphics getGraphics()

This method returns a Graphics instance that renders to this Image. This method is supported only for application-created offscreen images. In particular, images that represent external image data, like those returned from the getImage() methods in Applet and Toolkit, will throw an Illegal-AccessError from this method.

BufferedImage , as a subclass of Image, also has a getGraphics() method. However, it is deprecated. You should use the createGraphics() method instead, as it explicitly returns a Graphics2D instead of a Graphics:

public Graphics2D createGraphics()

Use this method to obtain a Graphics2D that represents this BufferedImage as a drawing surface.

The following example shows the two-faced nature of Images. It creates an image, draws on it, and then renders the modified image to the screen. It demonstrates that an image can be rendered on a drawing surface as well as being a drawing surface itself.

import java.awt.*; import java.awt.event.*; import java.awt.image.*; import java.io.*; import com.sun.image.codec.jpeg.*; public class ImageDuplicity extends Component { public static void main(String[] args) { ApplicationFrame f = new ApplicationFrame("ImageDuplicity v1.0"); f.setLayout(new BorderLayout()); Component ...