Question

i am having a scaling operation performed in the below code. The two sliders in the form are X and Y parameters for an scaling affine transformation. My ask here is when i change the slider the image is getting scaled, how do i dynamically resize my jpanel in which this image is getting painted.

/*
     * To change this template, choose Tools | Templates
     * and open the template in the editor.
     */
    package newpackage;

    import java.awt.Graphics;
    import java.awt.Image;
    import java.awt.geom.AffineTransform;
    import java.awt.image.AffineTransformOp;
    import java.awt.image.BufferedImage;
    import java.io.File;
    import java.io.IOException;
    import java.util.logging.Level;
    import java.util.logging.Logger;
    import javax.imageio.ImageIO;

    /**
     *
     * @author ABC
     */
    public class Swon extends javax.swing.JFrame {

        final BufferedImage img;
        /**
         * Creates new form Swon
         */
        public Swon() throws IOException{
           BufferedImage im=ImageIO.read(new File("C:/Users/ABC/Desktop/I-RIX2012_Final_logo_out.jpg"));
           this.img=new BufferedImage(im.getWidth(),im.getWidth(),BufferedImage.TYPE_BYTE_GRAY);
           this.img.getGraphics().drawImage(im, 0, 0, null);
            initComponents();
        }

        /**
         * This method is called from within the constructor to initialize the form.
         * WARNING: Do NOT modify this code. The content of this method is always
         * regenerated by the Form Editor.
         */
        @SuppressWarnings("unchecked")
        // <editor-fold defaultstate="collapsed" desc="Generated Code">
        private void initComponents() {

            jPanel1 = new javax.swing.JPanel(){

                // @Override

                //    public void paint(Graphics g)
                //    {
                    //        super.paint(g);
                    //        g.drawImage(img.getScaledInstance(this.getWidth(), this.getHeight(), Image.SCALE_FAST),0,0,null);
                    //    }

            };
            jSlider1 = new javax.swing.JSlider();
            jSlider2 = new javax.swing.JSlider();

            setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

            jPanel1.setBorder(new javax.swing.border.SoftBevelBorder(javax.swing.border.BevelBorder.RAISED));
            jPanel1.addComponentListener(new java.awt.event.ComponentAdapter() {
                public void componentResized(java.awt.event.ComponentEvent evt) {
                    jPanel1ComponentResized(evt);
                }
            });

            javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
            jPanel1.setLayout(jPanel1Layout);
            jPanel1Layout.setHorizontalGroup(
                jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGap(0, 268, Short.MAX_VALUE)
            );
            jPanel1Layout.setVerticalGroup(
                jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGap(0, 209, Short.MAX_VALUE)
            );

            jSlider1.setMaximum(5);
            jSlider1.setValue(1);
            jSlider1.addChangeListener(new javax.swing.event.ChangeListener() {
                public void stateChanged(javax.swing.event.ChangeEvent evt) {
                    jSlider1StateChanged(evt);
                }
            });

            jSlider2.setMaximum(5);
            jSlider2.setValue(1);
            jSlider2.addChangeListener(new javax.swing.event.ChangeListener() {
                public void stateChanged(javax.swing.event.ChangeEvent evt) {
                    jSlider2StateChanged(evt);
                }
            });

            javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
            getContentPane().setLayout(layout);
            layout.setHorizontalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGap(45, 45, 45)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jSlider2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jSlider1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                    .addContainerGap(242, Short.MAX_VALUE))
            );
            layout.setVerticalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGap(36, 36, 36)
                    .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGap(33, 33, 33)
                    .addComponent(jSlider1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(jSlider2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addContainerGap(38, Short.MAX_VALUE))
            );

            pack();
        }// </editor-fold>

        private void jPanel1ComponentResized(java.awt.event.ComponentEvent evt) {
            // TODO add your handling code here:
          //  AffineTransform f=new AffineTransform();

        }

        private void jSlider1StateChanged(javax.swing.event.ChangeEvent evt) {
            // TODO add your handling code here:

                        AffineTransform scale = AffineTransform.getScaleInstance(jSlider1.getValue(),jSlider2.getValue());       
                    AffineTransformOp op3 = new AffineTransformOp(scale, AffineTransformOp.TYPE_BILINEAR);
                    BufferedImage scaling = new BufferedImage(this.img.getHeight(), this.img.getWidth(), this.img.getType());
                    BufferedImage img1=op3.filter(this.img, scaling);
                    jPanel1.getGraphics().drawImage(img1.getScaledInstance(jPanel1.getWidth(), jPanel1.getHeight(), Image.SCALE_FAST), 0, 0, null);
        }

        private void jSlider2StateChanged(javax.swing.event.ChangeEvent evt) {
            // TODO add your handling code here:
             AffineTransform scale = AffineTransform.getScaleInstance(jSlider1.getValue(),jSlider2.getValue());       
                    AffineTransformOp op3 = new AffineTransformOp(scale, AffineTransformOp.TYPE_BILINEAR);
                    BufferedImage scaling = new BufferedImage(this.img.getHeight(), this.img.getWidth(), this.img.getType());
                    BufferedImage img1=op3.filter(this.img, scaling);
                    jPanel1.getGraphics().drawImage(img1.getScaledInstance(jPanel1.getWidth(), jPanel1.getHeight(), Image.SCALE_FAST), 0, 0, null);
        }

        /**
         * @param args the command line arguments
         */
        public static void main(String args[]) {
            /* Set the Nimbus look and feel */
            //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
            /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
             * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
             */
            try {
                for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                    if ("Nimbus".equals(info.getName())) {
                        javax.swing.UIManager.setLookAndFeel(info.getClassName());
                        break;
                    }
                }
            } catch (ClassNotFoundException ex) {
                java.util.logging.Logger.getLogger(Swon.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (InstantiationException ex) {
                java.util.logging.Logger.getLogger(Swon.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (IllegalAccessException ex) {
                java.util.logging.Logger.getLogger(Swon.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (javax.swing.UnsupportedLookAndFeelException ex) {
                java.util.logging.Logger.getLogger(Swon.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            }
            //</editor-fold>

            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    try {
                        new Swon().setVisible(true);
                    } catch (IOException ex) {
                        Logger.getLogger(Swon.class.getName()).log(Level.SEVERE, null, ex);
                    }
                }
            });
        }
        // Variables declaration - do not modify
        public javax.swing.JPanel jPanel1;
        private javax.swing.JSlider jSlider1;
        private javax.swing.JSlider jSlider2;
        // End of variables declaration
    }

Answer 1

Alright, firstly, don’t do this.img.getGraphics().drawImage(im, 0, 0, null), when the panel is repainted, the image would not be updated. You need to override the paintComponent method of a JComponent (prefer JPanel) and repaint the image at the appropriate scale.

Secondly, you need to place the image panel onto a layout that is capable of actually caring about the size of the panel (such as GridBagLayout). To do this, override the getPreferredSize method and return the size of the scaled image…

public class ResizableImagePane {

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

    public ResizableImagePane() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException ex) {
                } catch (InstantiationException ex) {
                } catch (IllegalAccessException ex) {
                } catch (UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new ScalerPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    protected class ScalerPane extends JPanel {
        private JSlider slider;
        private ImagePane imagePane;
        public ScalerPane() {

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();

            gbc.gridx = 0;
            gbc.gridy = 0;

            imagePane = new ImagePane();

            add(imagePane, gbc);

            gbc.gridy = 1;
            gbc.weightx = 0;
            gbc.weighty = 0;
            gbc.fill = GridBagConstraints.HORIZONTAL;

            slider = new JSlider();
            slider.setMinimum(1);
            slider.setMaximum(100);
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.anchor = GridBagConstraints.SOUTH;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            add(slider, gbc);

            slider.addChangeListener(new ChangeListener() {
                @Override
                public void stateChanged(ChangeEvent ce) {
                    imagePane.setZoom(slider.getValue() / 100f);
                }
            });
            slider.setValue(100);
        }
    }

    protected class ImagePane extends JPanel {
        private BufferedImage background;
        private Image scaled;
        private float zoom;
        public ImagePane() {
            try {
                background = ImageIO.read(new File("path/to/your/image"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            setZoom(1f);
            setBorder(new LineBorder(Color.RED));
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(scaled.getWidth(this), scaled.getHeight(this));
        }

        public void setZoom(float zoom) {
            this.zoom = zoom;
            int width = Math.round(background.getWidth() * zoom);
            scaled = background.getScaledInstance(width, -1, Image.SCALE_SMOOTH);

            invalidate();
            revalidate();
            repaint();
        }

        public float getZoom() {
            return zoom;
        }

        @Override
        protected void paintComponent(Graphics grphcs) {
            super.paintComponent(grphcs);

            int x = (getWidth() - scaled.getWidth(this)) / 2;
            int y = (getHeight() - scaled.getHeight(this)) / 2;

            grphcs.drawImage(scaled, x, y, this);
        }
    }
}