Java旋转图像

Question

   @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2=(Graphics2D) g.create();

        //rotation of player
         if(player.newDirection)
         {
             int rotationX=player.getImage().getWidth(null)/2;
             int rotationY=player.getImage().getHeight(null)/2;

             AffineTransform at=new AffineTransform();




                if(player.direction==LEFT)
                {
                    //graphics.rotate(Math.toRadians(90),bufferedImage.getWidth()/2,bufferedImage.getHeight()/2);
                    //graphics.drawImage(player.getImage(), player.getX(), player.getY(), null);
                    at.setToRotation(Math.toRadians(45), rotationX, rotationY);
                    g2.setTransform(at);
                    g2.drawImage(player.getImage(),player.getX(),player.getY(),null);
                    g2.dispose();
                    System.out.println("sola");
                }

I am trying to rotate the image of player but it does not work. Where is the problem?

Answer 1

I think I understand your problem.

Rotation are made around the (0, 0) point, so if you print your image in the middle of the screen, it will display very far away from where you'd think.

In order to have things work as expected, draw your image so that the center of the image will be at (0, 0), then translate it.

So you might have to do the transform as so: - Translate so that image center is (0, 0) - Rotate your image - Translate your image back to the required point

Answer 2

you might consider two other things when using the affirm transform...

when you code g2.setTransform(at); you must be very careful, because you set the affirmTransform for your entire graphics now! (see http://docs.oracle.com/javase/7/docs/api/java/awt/Graphics2D.html#setTransform%28java.awt.geom.AffineTransform%29 : it says: "This method should never be used to apply a new coordinate transform on top of an existing transform..." ) so don't make any mistakes there...

better use g2.drawImage(Image, at, ImageObserver) as noticed on http://docs.oracle.com/javase/7/docs/api/java/awt/Graphics2D.html

Another common mistake is to create a 'wrong' startOf-AffirmeTransform... i suggest you try to get one by AffineTransform at = AffineTransform.getRotateInstance(theta, cx,cy); and maybe concate another translate instance at.concatenate(AffineTransform.getTranslateInstance(dx, dy); or simply use at.translate(dx, dy) ... but remember: it's important in what order oyu performe transformations on your affineTransformation (its a differt if you [rotate and then translate] or [translat and then rotate] - just as a hint)...