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ID	CS001263	Creation date	January 7, 2009
Platform	Series 40 3rd Edition, FP1, S60 3rd Edition, S60 3rd Edition, FP1, S60 3rd Edition, FP2	Tested on devices	Nokia 6131, Nokia E70
Category	Java ME	Subcategory	Graphics

Keywords (APIs, classes, methods, functions): javax.microedition.lcdui.Image, javax.microedition.lcdui.game.Sprite, javax.microedition.lcdui.Image.createImage

Overview

This code snippet demonstrates how to rotate images in Java ME applications.

To rotate an image to a specified angle, a new image must be created by calling Image.createImage(Image sourceImage, int x, int y, int width, int height, int transform) method with source image passed as the sourceImage parameter and angle value passed as the transform parameter.

Some possible values of transform parameter are:

1. Sprite.TRANS_NONE - causes the specified image region to be copied unchanged
2. Sprite.TRANS_ROT90 - causes the specified image region to be rotated clockwise by 90 degrees.
3. Sprite.TRANS_ROT180 - causes the specified image region to be rotated clockwise by 180 degrees.
4. Sprite.TRANS_ROT270 - causes the specified image region to be rotated clockwise by 270 degrees.

Source file: ImageRotating.java

import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.game.Sprite;
 
import java.io.IOException;
 
 
public class ImageRotating extends MIDlet implements CommandListener {
 
    private Display display;
    // Form where image is placed
    private Form form;
 
    // Command for rotating source image.
    private Command cmdRotate0;
    private Command cmdRotate90;
    private Command cmdRotate180;
    private Command cmdRotate270;
    // Command for exiting from midlet.
    private Command cmdExit;
 
    private Image sourceImage;
    private Image destImage;    
 
    /**
     * Constructor
     */
    public ImageRotating() {
        initializeComponents();
 
        form.append(sourceImage);
    }
 
    /**
     * Initializes components of midlet 
     */
    private void initializeComponents() {
        // Get display
        display = Display.getDisplay(this);
 
        // Load image
        try {
            sourceImage = Image.createImage("/image.jpg");
        } catch (IOException e) {
            exitMIDlet();
        }
 
        // Create form
        form = new Form("Image rotating");
 
        cmdRotate0 = new Command("Rotate 0", Command.SCREEN, 0);
        form.addCommand(cmdRotate0);
        cmdRotate90 = new Command("Rotate 90", Command.SCREEN, 0);
        form.addCommand(cmdRotate90);
        cmdRotate180 = new Command("Rotate 180", Command.SCREEN, 0);
        form.addCommand(cmdRotate180);
        cmdRotate270 = new Command("Rotate 270", Command.SCREEN, 0);
        form.addCommand(cmdRotate270);
        cmdExit = new Command("Exit", Command.EXIT, 0);
        form.addCommand(cmdExit);
 
        form.setCommandListener(this);
    }
 
    /**
     * Rotates image and display it in the form. 
     * @param rotateType - angle of rotation.
     */
    private void rotateImage(int transform) {
        destImage = Image.createImage(sourceImage, 0, 0, 
                sourceImage.getWidth(), sourceImage.getHeight(), transform);
        form.deleteAll();
        form.append(destImage);
    }    
 
    /**
     * From MIDlet.
     * Signals the MIDlet that it has entered the Active state.
     */    
    public void startApp() {
        display.setCurrent(form);
    }
 
    /**
     * From MIDlet.
     * Signals the MIDlet to enter the Paused state.
     */    
    public void pauseApp() {
        // No implementation required
    }
 
    /**
     * From MIDlet.
     * Signals the MIDlet to terminate and enter the Destroyed state.
     */    
    public void destroyApp(boolean unconditional) {
        // No implementation required
    }
 
    /**
     * Performs exit from midlet.
     */    
    private void exitMIDlet() {
        notifyDestroyed();
    }
 
    /**
     * From CommandListener.
     * Indicates that a command event has occurred on Displayable d.
     * @param cmd - a Command object identifying the command.
     * @param d - the Displayable on which this event has occurred.
     */    
    public void commandAction(Command cmd, Displayable d) {
        if(cmd == cmdRotate0) {
            rotateImage(Sprite.TRANS_NONE);
        } else if(cmd == cmdRotate90) {
            rotateImage(Sprite.TRANS_ROT90);
        } else if(cmd == cmdRotate180) {
            rotateImage(Sprite.TRANS_ROT180);
        } else if(cmd == cmdRotate270) {
            rotateImage(Sprite.TRANS_ROT270);
        } else if(cmd == cmdExit) {
            exitMIDlet();
        }
    }
}

Postconditions

After loading the snippet image, now rotated, is shown on display.

By selecting the menu commands "Rotate 0" - "Rotate 270" the user can rotate the source image to a specific angle. After this, the rotated image will be shown on display.

Supplementary material

Executables and source files can be found here: RotatingImages.zip