Question

I’m trying to rotate an image, but it’s getting slightly messed up when I’m rotating it, and it looks like it’s not rotating it on center. So if I go around it looks like it’s being truncated. Is there a better method to get the “center” of the image?

public void RotateImageLeft() {
    try {
        BufferedImage newImage = new BufferedImage(originalImage.getWidth(), originalImage.getHeight(), originalImage.getType());
        AffineTransform tx = new AffineTransform();
        tx.rotate(Math.toRadians(-90.0), originalImage.getWidth() / 2, originalImage.getHeight() / 2);



        Graphics2D g2 = newImage.createGraphics();
        g2.drawImage(originalImage, tx, null);

        originalImage = newImage;


        this.repaint();

        g2.dispose();
    } catch (Exception ex) {
        ex.toString();
    }


    //g2d.drawImage(getResImage(), rescale, x, y);


}

For full code disclosure, here’s more code. Here’s my painComponent overridden method:

public void paintComponent(Graphics g) {
    super.paintComponent(g);
    resizeImage();

    Graphics2D g2d = (Graphics2D) g;
    g2d.drawImage(getResImage(), rescale, x, y);


}

Here’s the resizeImage() method that gets called:

public void resizeImage() {
    Graphics g = getResImage().getGraphics();
    g.setColor(Color.WHITE);

    g.fillRect(0, 0, getResImage().getWidth(), getResImage().getHeight());
    int scaledWidth = (int) ((getOriginalImage().getWidth() * getHeight()
            / getOriginalImage().getHeight()));
    if (scaledWidth < getWidth()) {
        int leftOffset = getWidth() / 2 - scaledWidth / 2;
        int rightOffset = getWidth() / 2 + scaledWidth / 2;

        g.drawImage(getOriginalImage(),
                leftOffset, 0, rightOffset, getHeight(),
                0, 0, getOriginalImage().getWidth(), getOriginalImage().getHeight(),
                null);
    } else {
        int scaledHeight = (getOriginalImage().getHeight() * getWidth())
                / getOriginalImage().getWidth();

        int topOffset = getHeight() / 2 - scaledHeight / 2;
        int bottomOffset = getHeight() / 2 + scaledHeight / 2;

        g.drawImage(getOriginalImage(),
                0, topOffset, getWidth(), bottomOffset,
                0, 0, getOriginalImage().getWidth(), getOriginalImage().getHeight(),
                null);
    }
}

I’m using the ResizeImage method since I want any image to fit correctly on my 720/432 panel.

Here’s some example pictures.
Pre-rotated

Post-rotated:

New code: (new image is the correct height/width of rotated image, still getting black bars. Screens below.

public void RotateImageLeft() {
    try {
        BufferedImage newImage = new BufferedImage( originalImage.getHeight(),originalImage.getWidth(), originalImage.getType());
        AffineTransform tx = new AffineTransform();
        tx.rotate(Math.toRadians(-90.0), newImage.getWidth() / 2, (newImage.getHeight() / 2));
        Graphics2D g2 = newImage.createGraphics();
        g2.drawImage(originalImage, tx, null);
        originalImage = newImage;
        this.repaint();
        g2.dispose();
    } catch (Exception ex) {
        ex.toString();
    }
}

Post rotate:

Answer 1

From my answer to another similar question

If you’re rotating then this will work for 90 degrees.

• move image so centered “around” the origin
• plain rotate() call with no extra parameters
• Move image back into the center remembering that now width = old height and height = old width.

Also remember the affine transform steps work in reverse order.

AffineTransform tx = new AffineTransform();

// last, width = height and height = width
tx.translate(originalImage.getHeight() / 2,originalImage.getWidth() / 2);
tx.rotate(Math.PI / 2);
// first - center image at the origin so rotate works OK
tx.translate(-originalImage.getWidth() / 2,-originalImage.getHeight() / 2);