Is there a way to resize images when loaded? The images are linked to a JList

Question

This is the code I wrote. It works only problem I can't resize the images. I've tried out getScaledInstance wasn't working. Any ideas on how to fix this. Also, why did I have to use a container to show the pictures shouldn't the panels be enough to show the results but until I added the container I wasn't getting any outputs.

package split;

import javax.swing.event.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.Container;

public class Split extends JFrame implements ListSelectionListener{
   
    JFrame f;
    JSplitPane s1;
    JList list1;
    JPanel listP,ImgP;
    JLabel img;
    Container contentPane;
   
   
    String a[] = {"Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"};
   
    Split(){
        list1 = new JList(a);
        list1.addListSelectionListener(new ListSelectionListener(){
            @Override
            public void valueChanged(ListSelectionEvent e) {
                switch(list1.getSelectedIndex()){
                case 0:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Mercury_profile_MDIS_MESSENGER.jpg"));
                    break;
                case 1:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Venus_from_Mariner_10.jpg"));
                    break;
                case 2:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download.jpg"));
                    break;
                case 3:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download (1).jpg"));
                    break;
                case 4:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Jupiter_and_its_shrunken_Great_Red_Spot.jpg"));
                    break;
                case 5:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download (2).jpg"));
                    break;
                case 6:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\download (3).jpg"));
                    break;
                case 7:
                    img.setIcon(new ImageIcon("C:\\Users\\DELL\\Desktop\\Planets\\Neptune_-_Voyager_2_(29347980845)_flatten_crop.jpg"));
                    break;
                }
               
            }
       
        });
        listP = new JPanel();
        listP.add(list1);
       
        img = new JLabel();
        ImgP = new JPanel();
        ImgP.add(img);
       
        s1 = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,listP, ImgP);
        s1.setOneTouchExpandable(true);
        s1.setDividerLocation(150);
        contentPane = getContentPane();
        contentPane.add(s1);
       
        setSize(500,500);
        setVisible(true);
   
       
                }

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

    @Override
    public void valueChanged(ListSelectionEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
   
}

Do any of these help? [Resizing image in Java](https://stackoverflow.com/questions/5895829/resizing-image-in-java) , [Resize a picture to fit a JLabel](https://stackoverflow.com/questions/16343098/resize-a-picture-to-fit-a-jlabel) , [How to resize JLabel ImageIcon](https://stackoverflow.com/questions/6714045/how-to-resize-jlabel-imageicon). There are lots more. Just enter **[swing] resize image** into the search box at the top of this Web page. — Abra, Mar 19 '22 at 06:41
(1-) *I've tried out getScaledInstance wasn't working.* - of course its not working. Your code doesn't even use that method. How do you expect us to comment on the code when we can't even see the code that uses the method in question??? — camickr, Mar 19 '22 at 13:39

score 1 · Answer 1 · answered Mar 19 '22 at 07:31

When using a JList, any resizing that is required can be done in the renderer. E.G. the images in the list on the left are 10% of the size of the main view when selected.

Here is the renderer:

class ScaledImageListCellRenderer extends DefaultListCellRenderer {

    @Override
    public Component getListCellRendererComponent(
            JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
        Component c = super.getListCellRendererComponent(
                list, value, index, isSelected, cellHasFocus);

        JLabel l = (JLabel)c;
        BufferedImage bi = (BufferedImage)value;
        int w = bi.getWidth();
        int h = bi.getHeight();
        String s = w + "x" + h;
        l.setText(s);
        l.setIcon(new ImageIcon(bi.getScaledInstance(w/10, h/10, BufferedImage.SCALE_FAST)));

        return l;
    }
};

Here is the self-contained source code that uses the renderer:

import java.awt.*;
import java.awt.image.*;
import java.util.Random;
import javax.swing.*;
import javax.swing.event.*;

public class ScaleBigImages {
    int sz = 50;
    int s = 10;
    Random random = new Random();
    JLabel imageLabel = new JLabel();

    ScaleBigImages() {
        init();
    }

    protected final void init() {
        JPanel gui = new JPanel(new BorderLayout(2,2));
        JList list = new JList();
        gui.add(new JScrollPane(list), BorderLayout.LINE_START);
        DefaultListModel dlm = new DefaultListModel();
        for (int ii=0; ii<19; ii++) {
            dlm.addElement(getBigImage());
        }
        list.setModel(dlm);
        list.setCellRenderer(new ScaledImageListCellRenderer());
        imageLabel.setIcon(new ImageIcon(new BufferedImage(
                s*sz,s*sz, BufferedImage.TYPE_INT_ARGB)));
        JPanel center = new JPanel(new GridBagLayout());
        center.add(imageLabel);
        gui.add(center);
        ListSelectionListener lsl = new ListSelectionListener() {
            @Override
            public void valueChanged(ListSelectionEvent e) {
                BufferedImage bi = (BufferedImage) list.getSelectedValue();
                imageLabel.setIcon(new ImageIcon(bi));
            }
        };
        list.addListSelectionListener(lsl);
        list.getSelectionModel().setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

        JFrame f = new JFrame("Scale Big Images");
        f.setLocationByPlatform(true);
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        f.add(gui);
        f.pack();
        f.setMinimumSize(f.getSize());
        f.setVisible(true);
    }

    class ScaledImageListCellRenderer extends DefaultListCellRenderer {

        @Override
        public Component getListCellRendererComponent(
                JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
            Component c = super.getListCellRendererComponent(
                    list, value, index, isSelected, cellHasFocus);

            JLabel l = (JLabel)c;
            BufferedImage bi = (BufferedImage)value;
            int w = bi.getWidth();
            int h = bi.getHeight();
            String s = w + "x" + h;
            l.setText(s);
            l.setIcon(new ImageIcon(bi.getScaledInstance(w/10, h/10, BufferedImage.SCALE_FAST)));

            return l;
        }
    };

    private BufferedImage getBigImage() {
        int w = s*sz;
        int h = s*sz;
        int r = random.nextInt(s/2);
        if (random.nextBoolean()) {
            w -= r*sz;
        } else {
            h -= r*sz;
        }

        return new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                new ScaleBigImages();
            }
        };
        SwingUtilities.invokeLater(r);
    }
}

MadProgrammer · Answer 2 · 2022-03-19T06:54:20.310

I might suggest using a JScrollPane, which would allow your JLabel/image to occupy more space then is currently available to the window, for example...

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

public final class Main {

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

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new Split();
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class Split extends JFrame {

        public Split() {
            String a[] = {"Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"};
            JList list1 = new JList(a);
            final JLabel img = new JLabel();
            list1.addListSelectionListener(new ListSelectionListener() {
                @Override
                public void valueChanged(ListSelectionEvent e) {
                    if (e.getValueIsAdjusting()) {
                        return;
                    }
                    try {
                        switch (list1.getSelectedIndex()) {
                            case 0:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute1.png"))));
                                break;
                            case 1:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute2.png"))));
                                break;
                            case 2:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute3.png"))));
                                break;
                            case 3:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute4.png"))));
                                break;
                            case 4:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute5.png"))));
                                break;
                            case 5:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute6.png"))));
                                break;
                            case 6:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute7.png"))));
                                break;
                            case 7:
                                img.setIcon(new ImageIcon(ImageIO.read(getClass().getResource("/images/Cute8.png"))));
                                break;
                        }
                    } catch (IOException ex) {
                        JOptionPane.showMessageDialog(img, "Could not load image", "Error", JOptionPane.ERROR_MESSAGE);
                    }

                }

            });

            JPanel basePane = new JPanel(new BorderLayout()) {
                @Override
                public Dimension getPreferredSize() {
                    return new Dimension(400, 400);
                }
            };
            basePane.add(new JScrollPane(img));

            JSplitPane s1 = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, new JScrollPane(list1), basePane);
            s1.setOneTouchExpandable(true);
            s1.setDividerLocation(150);

            add(s1);
        }

    }
}

See How to Use Scroll Panes for more details.

You should also learn to make use of ImageIO.read, it will save you a lot of issues and hair pulling in the long run, see Reading/Loading an Image

If you still want to resize the image, then you could also have a look at ...

as few examples

Is there a way to resize images when loaded? The images are linked to a JList

2 Answers2