Java, JPanel crop image while rotating

Question

i am making simple image editor in java. My problem is that when i rotate image its being cropped, i will try to show it on images:

before rotation https://i.stack.imgur.com/Rk2Un.jpg

after 45 degre https://i.stack.imgur.com/phUuZ.jpg

after 90 degrees rotation i[dot]imgur[dot]com/4NrABIA.jpg

It looks like JPanel crops rotated image into size of original image, i dont know why :/ so i am asking for help. Thank you.

Heres my code:

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener;
import javax.swing.*;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import static java.awt.image.ImageObserver.WIDTH;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JPanel;
import javax.swing.filechooser.FileFilter;
import javax.swing.filechooser.FileNameExtensionFilter;

public class OknoInterfejsu extends JFrame{

Container content;
BufferedImage image = null;
JLabel picLabel;
Image scaledImage;
private final JButton przyciski[];
private JComboBox wybor;
private String wybor_str[];
private int picHeight;
private int picWidth;
private int realHeight;
double picAspect;
private String path;


private class ObslugaPrzycisku implements ActionListener{

   private final JFrame ref_okno;

   ObslugaPrzycisku(JFrame okno){
        ref_okno = okno;
   }

   public void actionPerformed(ActionEvent e) {
        JButton bt = (JButton)e.getSource();
        if(bt==przyciski[0]){
           //-----------WCZYTAJ PRZYCISK-------------
        {
            JFileChooser fileChooser = new JFileChooser("C:\\Users\\Filip\\Pictures\\");
            FileFilter imageFilter = new FileNameExtensionFilter(
             "Image files", ImageIO.getReaderFileSuffixes());
            fileChooser.setFileFilter(imageFilter);
             if (fileChooser.showOpenDialog(null)==JFileChooser.APPROVE_OPTION)
             {
                 File plik = fileChooser.getSelectedFile();
                 path = plik.getPath();
                 System.out.print(path);
                try {
                    image = ImageIO.read(new File(path));
                } catch (IOException ex) {
                    Logger.getLogger(OknoInterfejsu.class.getName()).log(Level.SEVERE, null, ex);
                }

               picHeight = image.getHeight();
               picWidth = image.getWidth();
               picAspect = (double) picHeight / picWidth;
               //if(picAspect>1)realHeight = 400;
               //else realHeight = 800;
               realHeight = 400;
                scaledImage = image.getScaledInstance(realHeight, (int) (realHeight*picAspect),Image.SCALE_SMOOTH);

                picLabel = new JLabel(new ImageIcon(scaledImage));

                content.add(picLabel);
               content.revalidate();
               content.repaint();

             }

        } 
        }
          //--------------------------OBROT +------------  
         else if(bt==przyciski[1]){
            picLabel.setIcon(null);

            int temp1 = (int) (400*picAspect);

            picRotate(scaledImage, 400,temp1);

            picLabel = new JLabel(new ImageIcon(scaledImage));
               content.add(picLabel);
               content.revalidate();
               content.repaint();
        }   


   }
   }

    public OknoInterfejsu()
   {    
    super("Okno interfejsu");


    setSize(1000,700);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

   //-------------------------------------------------------
    przyciski = new JButton[2];
    przyciski[0] = new JButton("Wczytaj Obraz");
    przyciski[0].addActionListener(new ObslugaPrzycisku(this));

    przyciski[1] = new JButton("Obrót +");
    przyciski[1].addActionListener(new ObslugaPrzycisku(this));

    JPanel panelPrzyciski   = new JPanel(new FlowLayout());
    panelPrzyciski.add(przyciski[0]);
    panelPrzyciski.add(przyciski[1]);

    //-------------------------------------------------------
    content  = getContentPane();
    content.setLayout(new BorderLayout());
    content.add(panelPrzyciski,BorderLayout.SOUTH);

    setVisible(true);
    }



     public static void main(String args[]){
     new OknoInterfejsu();
    }

    public void picRotate(Image image,int w,int h){

    BufferedImage temp=(BufferedImage)createImage(w,h);
    Graphics2D  g2d=(Graphics2D)temp.createGraphics(); 
    g2d.rotate((Math.PI/2)*22.5, w/2, h/2);

    g2d.drawImage(image,0,0,null); 
    this.scaledImage=temp; 
    g2d.dispose();  


    }
    }

The [second example from this answer](https://stackoverflow.com/questions/15779877/rotate-bufferedimage-inside-jpanel/15780090#15780090) will create a new image sized to fit the rotated image — MadProgrammer, May 23 '17 at 20:11
And if you're having trouble figuring out which piece of code you're suppose to be looking at [here it is broken down](https://stackoverflow.com/questions/30204114/rotating-an-image-object/30204975#30204975) — MadProgrammer, May 23 '17 at 20:14

MadProgrammer · Accepted Answer · 2020-05-25T13:25:36.470

When you rotate an image, it changes size, you need to create a new image whose bounds encompass this new size, for example

public Image rotateBy(Image image, double degrees) {

    // The size of the original image
    int w = source.getWidth();
    int h = source.getHeight();
    // The angel of the rotation in radians
    double rads = Math.toRadians(degrees);
    // Some nice math which demonstrates I have no idea what I'm talking about
    // Okay, this calculates the amount of space the image will need in
    // order not be clipped when it's rotated
    double sin = Math.abs(Math.sin(rads));
    double cos = Math.abs(Math.cos(rads));
    int newWidth = (int) Math.floor(w * cos + h * sin);
    int newHeight = (int) Math.floor(h * cos + w * sin);

    // A new image, into which the original can be painted
    BufferedImage rotated = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2d = rotated.createGraphics();
    // The transformation which will be used to actually rotate the image
    // The translation, actually makes sure that the image is positioned onto
    // the viewable area of the image
    AffineTransform at = new AffineTransform();
    at.translate((newWidth - w) / 2, (newHeight - h) / 2);

    // And we rotate about the center of the image...
    int x = w / 2;
    int y = h / 2;
    at.rotate(rads, x, y);
    g2d.setTransform(at);
    // And we paint the original image onto the new image
    g2d.drawImage(image, 0, 0, null);
    g2d.dispose();

    return rotated;
}

Then you just need to call it...

picLabel.setIcon(new ImageIcon(rotateBy(scaledImage, 22.5)));

Because setIcon is a bound property, it should trigger a layout and paint pass automatically, if not, you can simply call revalidate and repaint to trigger them manually

omg, you gave me done solution, thank you very much, at the moment it doesnt work for me, but i believe its fine, i just have to understand it and force it to show rotated image, i use revalidate and repaint — lifififi, May 23 '17 at 20:57
Yes it works, my problem was that i badly changed your code :/ nevermind, it works nicely, but only once, i cant rotate image further :/ — lifififi, May 23 '17 at 21:05
The rotation is based on the source image, in this case `scaledImage`, which obviously never changes (this is not a bad thing), what I would do is maintain a variable which defined the current rotation angle, each time you want to rotate the image, update this variable and pass it to the `rotateBy` method — MadProgrammer, May 23 '17 at 22:20
oohh it was so simple, thank You very much! Works like a charm now. — lifififi, May 24 '17 at 06:55

score 0 · Answer 2 · answered May 23 '17 at 20:21

I see you're using picLabel to store the image and display it:

     picRotate(scaledImage, 400,temp1);

        picLabel = new JLabel(new ImageIcon(scaledImage));
           content.add(picLabel);
           content.revalidate();
           content.repaint();

For some reason label size is the Image height and width but label doesn't know the image was rotated. A work around this might be to set the size of the label prior to adding the image to it, and have a way to guaranteed that the size will accommodate the whole image even if is rotated:

     picRotate(scaledImage, 400,temp1);

        picLabel = new JLabel();
           picLabel.setPreferredSize(new Dimension(800, 800));
           picLabel.add(new ImageIcon(scaledImage))
           content.add(picLabel);
           content.revalidate();
           content.repaint();

Now picLabel width and height in the preferred size has to be calculated based on the space needed by the rotated image. I thing some trigonometric functions might help for this. I'm assuming 800x800 is enough space to accommodate the image

Given the fact that they never change the size of the image might have something to do with it - and the fact that when they rotate the image , they apply it to a new instance of `JLabel` would also suggest that that's no the actual problem as `JLabel`'s preferred size is based on the size of the image and it's text property - so again, not the problem — MadProgrammer, May 23 '17 at 20:37

Java, JPanel crop image while rotating

2 Answers2