Scale the Imageicon Automatically to Label Size

Resize a picture to fit a JLabel

Outline

Here are the steps to follow.

• Read the picture as a BufferedImage.
• Resize the BufferedImage to another BufferedImage that's the size of the JLabel.
• Create an ImageIcon from the resized BufferedImage.

You do not have to set the preferred size of the JLabel. Once you've scaled the image to the size you want, the JLabel will take the size of the ImageIcon.

Read the picture as a BufferedImage

BufferedImage img = null;
try {
    img = ImageIO.read(new File("strawberry.jpg"));
} catch (IOException e) {
    e.printStackTrace();
}

Resize the BufferedImage

Image dimg = img.getScaledInstance(label.getWidth(), label.getHeight(),
        Image.SCALE_SMOOTH);

Make sure that the label width and height are the same proportions as the original image width and height. In other words, if the picture is 600 x 900 pixels, scale to 100 X 150. Otherwise, your picture will be distorted.

Create an ImageIcon

ImageIcon imageIcon = new ImageIcon(dimg);

How to dynamically scale an image when changing the size of the JLabel

I'd like to adjust the size of the image together with the size of the JLabel

You can use the Stretch Icon. It will scale automatically when the label size is changed. Works for any components that can display an Icon.

Then I surrounded the JLabel with a JScrollPane

However, when I reduce the windows size, the image is not being reduced in size but instead stays the same

You should not be using a JScrollPane. The size of the component added to the scroll pane doesn't change when the scroll pane shrinks. Instead scrollbars are displayed.

I'm using the provided GroupLayout and set the horizontal and vertical axes to "Auto-Resizable

I would not use an IDE to generate the layout code and I would not use GroupLayout as it is overly complex for something this simple.

Just add the label (using the StretchIcon) to the frame. By default the frame uses a BorderLayout which will automatically resize any component added to the CENTER of the BorderLayout.

How to resize JLabel ImageIcon?

Resizing the icon is not straightforward. You need to use Java's graphics 2D to scale the image. The first parameter is a Image class which you can easily get from ImageIcon class. You can use ImageIcon class to load your image file and then simply call getter method to get the image.

private Image getScaledImage(Image srcImg, int w, int h){
    BufferedImage resizedImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2 = resizedImg.createGraphics();

    g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g2.drawImage(srcImg, 0, 0, w, h, null);
    g2.dispose();

    return resizedImg;
}

Resizing image to fit in JLabel

BufferedImage img = ImageIO.read(...);
Image scaled = img.getScaledInstance(500, 500, Image.SCALE_SMOOTH);
ImageIcon icon = new ImageIcon(scaled);

Beware, that this will scale the image so that it is square. Take a look at Java: maintaining aspect ratio of JPanel background image which discusses maintaining the aspect ratio of the image when scaled.

Also, you should read The Perils of Image.getScaledInstance() and have a look at Scale the ImageIcon automatically to label size which uses a divide and conqure scaling algorithim and Quality of Image after resize very low -- Java which demonstrates the issues of doing a one step scale...

Resizing Image to fit jLabel Trouble

That image has transparency. So change BufferedImage.TYPE_INT_RGB to BufferedImage.TYPE_INT_ARGB

It is not obvious at SO on a white BG, but try this SSCCE & it becomes more clear..

import java.net.URL;
import javax.swing.*;

class ShowImage {

    public static void main(String[] args) throws Exception {
        final URL url = new URL("http://i.stack.imgur.com/1yeUy.png");
        Runnable r = new Runnable() {
            @Override
            public void run() {
                JLabel l = new JLabel(new ImageIcon(url));

                JOptionPane.showMessageDialog(null, l);
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}

scaling an image produce the error at java.awt.image.ReplicateScaleFilter. init (Unknown Source) )

JLabel label=new JLabel();
System.out.println( label.getSize() );

Try the above code.

I would guess the issue is that the size of the label is (0, 0), so it would be hard to scale an image to that size.

Instead you should pick the size that you want the image to be, then get the scaled instance and then create the label using the scaled image.

Edit:

I want to make the size of the image equal to the size of label whenever the user change the size of the window,

So you want the size of the image to dynamically scale. So you can't just create an initial scaled image.

Also you can't add the JLabel to a JPanel and then add the panel to the frame because the default layout manager of the JPanel is the FlowLayout, which will always respect the preferred size of the label.

So you have a couple of options:

1. Do custom painting on a JPanel. In the paintCompononent(...) method you would get the current size of the panel using the getWidth() and getHeight() methods of the JPanel. Then you would use the drawImage(...) method of the Graphics class to draw the image. This custom panel would then be added directly to BorderLayout.CENTER of the frame to allow the panel to dynamically resize. Read the Swing tutorial on Custom Painting for more information and working examples to get your started.

2. Use the Stretch Icon. This is a custom class that will allow the Icon to dynamically resize. So you would create the JLabel using the StretchIcon and then add the label to the BorderLayout.CENTER of the frame.

Resize label Icon

Try the following:

Change

jLabel1.setIcon(new javax.swing.ImageIcon(getClass().getResource("/org/me/musiconweb/resources/Music-icon.png")));

TO

BufferedImage img = null;
try {
    img = ImageIO.read(new File("/org/me/musiconweb/resources/Music-icon.png"));
} catch (IOException e) {
    e.printStackTrace();
}
BufferedImage dimg = img.getScaledInstance(label.width, label.height,
            Image.SCALE_SMOOTH);

jLabel1.setIcon(new javax.swing.ImageIcon(dimg));

Hope that works. :)

Also, please take into consideration what @MadProgrammer discussed about not using getScaledImage. Though, if I were in your shoes, I would do incremental phases, first trying this out and if this works, go ahead and use the Graphic.scaleImage method.

For more info follow Resize a picture to fit a JLabel

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