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Java Cookbook by Ian F. Darwin

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Drawing an Image

Problem

You want to display an image, a preformatted bitmap, or raster file.

Solution

Use the Graphics drawImage( ) method in your paint routine. Image objects represent bitmaps. They are normally loaded from a file via getImage( ), but can also be synthesized using createImage( ) . You can’t construct them yourself, however: the Image class is abstract. Once you have an image, displaying it is trivial:

// File graphics/DrawImageDemo.java 
public void paint(Graphics g) { 
    g.drawImage(0, 0, myImage, this); 
}

Discussion

You can get an image by using a routine named, naturally, getImage( ) . If your code will be used only in an applet, you can use the Applet method getImage( ), but if you want it to run in an application as well, you need to use the Toolkit version. This form takes either a filename or a URL. The filename, of course, when it turns up in an applet, will fail with a security exception unless the user installs a policy file. Program GetImage shows the code for doing this both ways:

/* * For Applet, invoke as: <APPLET CODE="GetImage" WIDTH="100" HEIGHT="100"> </APPLET> * For Application, just run it (has own main). */ import java.awt.*; import java.net.*; // for URL class /** This program, which can be an Applet or an Application, * shows a form of Toolkit.getImage( ) which works the same * in either Applet or Application! */ public class GetImage extends java.applet.Applet { Image image; public void init( ) { loadImage( ); } public void loadImage( ) { ...

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