Rotate BufferedImage shows black bound

Question

I want to rotate a bufferedImage. The code I use makes it possible that the image rotates. But it cuts the image to a square. The screen shows then a black "border" on the left and the right side.
If I use debugging tool, the image width is about the whole width included the black "border". But the black "border" don't rotate, it's always at the left and the right side. And the image is missing the picture-parts left and right. The squared-image isn't cut again if I rotate it again. If I change the src.getWidth()-parts the image will be smaller with each rotation.

  private static BufferedImage rotateImage(BufferedImage src, double degrees) {
      AffineTransform affineTransform = AffineTransform.getRotateInstance(
        Math.toRadians(degrees), (src.getWidth() / 2), (src.getHeight() / 2));

      BufferedImage rotatedImage = new BufferedImage(src.getWidth(), src.getHeight(), src.getType());
      Graphics2D g = (Graphics2D) rotatedImage.getGraphics();
      g.setTransform(affineTransform);
      g.drawImage(src, 0, 0, null);
      return rotatedImage;
  }

  public void rotateImage(int degree) {
     if (this.image != null) {
         this.setImage(myJComponent.rotateImage(this.image, degree));
     }
  }

1) For better help sooner, post an [MCVE](http://stackoverflow.com/help/mcve) (Minimal, Complete, Verifiable Example). 2) One way to get images for an example is to hot-link to images listed in [this Q&A](http://stackoverflow.com/q/19209650/418556). — Andrew Thompson, Aug 03 '14 at 12:17
You can find the enclosing upright boundary, as shown [here](http://stackoverflow.com/a/10644775/230513), and fill it with a preferred color. — trashgod, Aug 03 '14 at 13:30

score 2 · Accepted Answer · answered Aug 03 '14 at 14:06

The size of the image will change as you rotate it.

Here is some code to play with:

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;

public class Rotation
{
    BufferedImage image;
    JLabel label;

    public Rotation(BufferedImage image)
    {
        this.image = image;
    }

    private BufferedImage getImage(double theta)
    {
        //  Determine the size of the rotated image

        double cos = Math.abs(Math.cos(theta));
        double sin = Math.abs(Math.sin(theta));
        double width  = image.getWidth();
        double height = image.getHeight();
        int w = (int)(width * cos + height * sin);
        int h = (int)(width * sin + height * cos);

        //  Rotate and paint the original image onto a BufferedImage

        BufferedImage out = new BufferedImage(w, h, image.getType());
        Graphics2D g2 = out.createGraphics();
        g2.setPaint(UIManager.getColor("Panel.background"));
        g2.fillRect(0,0,w,h);
        double x = w/2;
        double y = h/2;
        AffineTransform at = AffineTransform.getRotateInstance(theta, x, y);
        x = (w - width)/2;
        y = (h - height)/2;
        at.translate(x, y);
        g2.drawRenderedImage(image, at);
        g2.dispose();
        return out;
    }

    private JLabel getLabel()
    {
        ImageIcon icon = new ImageIcon(image);
        label = new JLabel(icon);
        label.setHorizontalAlignment(JLabel.CENTER);
        return label;
    }

    private JSlider getSlider()
    {
        final JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 360, 0);
        slider.addChangeListener(new ChangeListener()
        {
            public void stateChanged(ChangeEvent e)
            {
                int value = slider.getValue();
                BufferedImage bi = getImage(Math.toRadians(value));
                label.setIcon(new ImageIcon(bi));
            }
        });
        return slider;
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                try
                {
                    String path = "mong.jpg";
                    ClassLoader cl = Rotation.class.getClassLoader();
                    BufferedImage bi = ImageIO.read(cl.getResourceAsStream(path));
                    Rotation r = new Rotation(bi);
                    JFrame f = new JFrame();
                    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    f.getContentPane().add(new JScrollPane(r.getLabel()));
                    f.getContentPane().add(r.getSlider(), "South");
                    f.pack();
                    f.setLocation(200,200);
                    f.setVisible(true);
                }
                catch(IOException e)
                {
                    System.out.println(e);
                }
            }
        });
    }
}

Just change the image you want to read and use the slider to rotate the image.

Rotate BufferedImage shows black bound

1 Answers1