Question

I am just wondering how to rotate a rectangle image with paintComponent() method of JLabel component and set its new width and height correctly?

I tried to rotate (see attached image) and the image scale becomes bigger but the JLabel scale keeps the same what makes image be out of JLabel bounds or something :S So my question is how to set image new width and height to component dynamically in a more optimal way?

Answer 1

OK I tried the sample David Kroukamp showed me. Thanks, David, you pointed me to right direction. I think it is a really good snippet to lean back on.

public static BufferedImage rotateImage(Image image, int angle)
    {
        double sin = Math.abs(Math.sin(angle));
        double cos = Math.abs(Math.cos(angle));
        int originalWidth = image.getWidth(null);
        int originalHeight = image.getHeight(null);
        int newWidth = (int) Math.floor(originalWidth * cos + originalHeight * sin);
        int newHeight = (int) Math.floor(originalHeight * cos + originalWidth * sin);
        BufferedImage rotatedBI = new BufferedImage(newWidth, newHeight, BufferedImage.TRANSLUCENT);
        Graphics2D g2d = rotatedBI.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.translate((newWidth - originalWidth) / 2, (newHeight - originalHeight) / 2);
        g2d.rotate(angle, originalWidth / 2, originalHeight / 2);
        g2d.drawImage(image, 0, 0, null);
        g2d.dispose();
        return rotatedBI;
    }

David Kroukamp’s result image preview

I tested the snippet and the result image + its component’s scale were really dynamic changed.
But the result component width I’ve got has been always a little bit wider than it’s inner image was :S

For example here is my version of an image rotated in 45 degrees angle

… As I could find (on blue background) its width is not totally fit to surround white image … Actually I was looking for some kind of standard Java Image Processing rotate solution but I couldn’t find it 🙁 so I had to dig deeper to the problem and at least figure out how to solve the ‘wider effect’ and avoid create new BufferedImage object every re-paint…

OK, as a reault of my research, I tried to write some kind of my rotate code adaptation. Here it is :

>tested

public static void rotateImage(Graphics g, Image image,int tilt,JComponent component)
    {

        // create the transform, note that the transformations happen

                  // in reversed order (so check them backwards)
                  AffineTransform at = new AffineTransform();

                  //5. modify component scale ...

                  double sin = Math.abs(Math.sin(Math.toRadians(tilt)));
                  double cos = Math.abs(Math.cos(Math.toRadians(tilt)));

                  int w=image.getWidth(null);
                  int h=image.getHeight(null);
                  int newW=(int) Math.floor(w * cos + h * sin);
                  int newH=(int) Math.floor(h * cos + w * sin);

                  component.setSize(newW, newH);

                  int width=component.getWidth();
                  int height=component.getHeight();

                  // 4. translate it to the center of the component
                  at.translate(width / 2, height / 2);

                  // 3. do the actual rotation
                  at.rotate(Math.toRadians(tilt));

                  // 2. just a scale because this image is big
    //              at.scale(1, 1);


                  // 1. translate the object so that you rotate it around the
                  //    center (easier :))
                  at.translate(-image.getWidth(null)/2, -image.getHeight(null)/2);



                  // draw the image
                  ((Graphics2D) g).drawImage(image, at, null);


        }

… so the result image rotated on -30 degrees tilt looks like this

I dearly hope the tip saves ones day 🙂

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Thank you all for help