How to add an image to a JPanel?
Asked Answered
B

14

371

I have a JPanel to which I'd like to add JPEG and PNG images that I generate on the fly.

All the examples I've seen so far in the Swing Tutorials, specially in the Swing examples use ImageIcons.

I'm generating these images as byte arrays, and are usually larger than the common icons they use in the examples, at 640x480.

  1. Is there any (performance or other) problem in using the ImageIcon class to display an image that size in a JPanel?
  2. What's the "usual" way of doing it?
  3. How to add an image to a JPanel without using the ImageIcon class?

Edit: A more careful examination of the tutorials and the API shows that you cannot add an ImageIcon directly to a JPanel. Instead, they achieve the same effect by setting the image as an icon of a JLabel. This just doesn't feel right...

Borodin answered 18/11, 2008 at 17:36 Comment(2)
Depending on how you are generating the byte arrays, it may more efficient to use a MemoryImageSource than to convert them to JPEG or PNG format and then read with ImageIO as most answers suggest. You could get an Image from a MemoryImageSource constructed with your image data by using createImage, and display as suggested in one of the answers.Erhard
Check my answer #43862491Taphole
L
267

Here's how I do it (with a little more info on how to load an image):

import java.awt.Graphics;
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;
import javax.swing.JPanel;

public class ImagePanel extends JPanel{

    private BufferedImage image;

    public ImagePanel() {
       try {                
          image = ImageIO.read(new File("image name and path"));
       } catch (IOException ex) {
            // handle exception...
       }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, this); // see javadoc for more info on the parameters            
    }

}
Loosetongued answered 18/11, 2008 at 17:50 Comment(7)
I tried using this with some custom buttons on top, and found that there were strange redrawing issues. Fred Haslam's answer, below, did not suffer from this problem.Fidelis
-1 for invalid implementation of paintComponent (@Fidelis most probably that's why you are having those redrawing issues) - it must garantee to cover its complete area if it reports being opaque (which is the default), easiest achieved by calling super.paintComponentAdalbertoadalheid
@kleopatra, Thanks, I didn't realize that... according to the javadoc: "Further, if you do not invoker super's implementation you must honor the opaque property, that is if this component is opaque, you must completely fill in the background in a non-opaque color. If you do not honor the opaque property you will likely see visual artifacts." I'll update the answer now.Loosetongued
Please always respect the Principle of Encapsulation while overriding methods of the Super Class, the Access Specifier of the paintComponent(...) method is protected and not public :-)Lecherous
This is no good, it doesn't do anything about sizing the panel to the image. More code will have to be added later do deal with this. Much simpler to use the JLabel answer.Tamarisk
@nIcEcOw is there any chance you'd be willing to cite a source on the Principals of Encapsulation?Clishmaclaver
@Jonathan: I am really sorry, regarding some source for Principle of Encapsulation. Just remember while programming, what should be hidden from the rest of the code, needs to be maintained that way, instead of being visible to everythingy in the code. Seems like it is one such thingy that comes with experience, as one learns each day. Any book can give a basic idea what encapsulation is, but it is how we implement our code that decides how much we adhering to the concept.Lecherous
A
552

If you are using JPanels, then are probably working with Swing. Try this:

BufferedImage myPicture = ImageIO.read(new File("path-to-file"));
JLabel picLabel = new JLabel(new ImageIcon(myPicture));
add(picLabel);

The image is now a swing component. It becomes subject to layout conditions like any other component.

Audrieaudris answered 25/4, 2010 at 0:46 Comment(7)
how to scale the image according to the size of the JLabel?Jornada
Nice code! I'm not much experienced with Swing but I can't get it work. Does anybody tried it in jdk 1.6.0_16?Atalanti
@Atalanti I know you asked this a while back but if any other newbies had my issues, remember to picLabel.setBounds();Furmark
Do I have to create new JLabel object each time when a photo is reloaded?Kattiekatuscha
I didn't have to do setBounds or anything. This code is awesome! The add(picLabel) was a bit vague... you need somethin to add to! If you're a newbie: either try this.add... or if you have a JFrame object X, then try X.add....Dodds
@Jornada new JLabel(new ImageIcon(backgroundImage.getScaledInstance(width, height, Image.SCALE_FAST)));Kilter
@Atalanti It's been a while since you asked that question. But maybe that will help others in the future. It didn't work for me as well. I used a .ico image. Then I tried a .png image and it worked for me. :)Mithraism
L
267

Here's how I do it (with a little more info on how to load an image):

import java.awt.Graphics;
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;
import javax.swing.JPanel;

public class ImagePanel extends JPanel{

    private BufferedImage image;

    public ImagePanel() {
       try {                
          image = ImageIO.read(new File("image name and path"));
       } catch (IOException ex) {
            // handle exception...
       }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, this); // see javadoc for more info on the parameters            
    }

}
Loosetongued answered 18/11, 2008 at 17:50 Comment(7)
I tried using this with some custom buttons on top, and found that there were strange redrawing issues. Fred Haslam's answer, below, did not suffer from this problem.Fidelis
-1 for invalid implementation of paintComponent (@Fidelis most probably that's why you are having those redrawing issues) - it must garantee to cover its complete area if it reports being opaque (which is the default), easiest achieved by calling super.paintComponentAdalbertoadalheid
@kleopatra, Thanks, I didn't realize that... according to the javadoc: "Further, if you do not invoker super's implementation you must honor the opaque property, that is if this component is opaque, you must completely fill in the background in a non-opaque color. If you do not honor the opaque property you will likely see visual artifacts." I'll update the answer now.Loosetongued
Please always respect the Principle of Encapsulation while overriding methods of the Super Class, the Access Specifier of the paintComponent(...) method is protected and not public :-)Lecherous
This is no good, it doesn't do anything about sizing the panel to the image. More code will have to be added later do deal with this. Much simpler to use the JLabel answer.Tamarisk
@nIcEcOw is there any chance you'd be willing to cite a source on the Principals of Encapsulation?Clishmaclaver
@Jonathan: I am really sorry, regarding some source for Principle of Encapsulation. Just remember while programming, what should be hidden from the rest of the code, needs to be maintained that way, instead of being visible to everythingy in the code. Seems like it is one such thingy that comes with experience, as one learns each day. Any book can give a basic idea what encapsulation is, but it is how we implement our code that decides how much we adhering to the concept.Lecherous
S
41

Fred Haslam's way works fine. I had trouble with the filepath though, since I want to reference an image within my jar. To do this, I used:

BufferedImage wPic = ImageIO.read(this.getClass().getResource("snow.png"));
JLabel wIcon = new JLabel(new ImageIcon(wPic));

Since I only have a finite number (about 10) images that I need to load using this method, it works quite well. It gets file without having to have the correct relative filepath.

Surfperch answered 27/12, 2010 at 6:49 Comment(2)
I substituted the first line with BufferedImage previewImage = ImageIO.read(new URL(imageURL)); to get my images from a server.Philosophize
For referring images from jar, try this https://mcmap.net/q/93455/-add-image-icons-to-buttons-labels-swingKonstanz
R
33

I think there is no need to subclass of anything. Just use a Jlabel. You can set an image into a Jlabel. So, resize the Jlabel then fill it with an image. Its OK. This is the way I do.

Restraint answered 3/10, 2009 at 19:7 Comment(0)
V
19

You can avoid rolling your own Component subclass completely by using the JXImagePanel class from the free SwingX libraries.

Download

Victuals answered 19/11, 2008 at 0:37 Comment(0)
C
11
JLabel imgLabel = new JLabel(new ImageIcon("path_to_image.png"));
Circumvent answered 4/5, 2013 at 21:40 Comment(0)
C
7

You can subclass JPanel - here is an extract from my ImagePanel, which puts an image in any one of 5 locations, top/left, top/right, middle/middle, bottom/left or bottom/right:

protected void paintComponent(Graphics gc) {
    super.paintComponent(gc);

    Dimension                           cs=getSize();                           // component size

    gc=gc.create();
    gc.clipRect(insets.left,insets.top,(cs.width-insets.left-insets.right),(cs.height-insets.top-insets.bottom));
    if(mmImage!=null) { gc.drawImage(mmImage,(((cs.width-mmSize.width)/2)       +mmHrzShift),(((cs.height-mmSize.height)/2)        +mmVrtShift),null); }
    if(tlImage!=null) { gc.drawImage(tlImage,(insets.left                       +tlHrzShift),(insets.top                           +tlVrtShift),null); }
    if(trImage!=null) { gc.drawImage(trImage,(cs.width-insets.right-trSize.width+trHrzShift),(insets.top                           +trVrtShift),null); }
    if(blImage!=null) { gc.drawImage(blImage,(insets.left                       +blHrzShift),(cs.height-insets.bottom-blSize.height+blVrtShift),null); }
    if(brImage!=null) { gc.drawImage(brImage,(cs.width-insets.right-brSize.width+brHrzShift),(cs.height-insets.bottom-brSize.height+brVrtShift),null); }
    }
Codfish answered 18/11, 2008 at 17:48 Comment(0)
O
7
  1. There shouldn't be any problem (other than any general problems you might have with very large images).
  2. If you're talking about adding multiple images to a single panel, I would use ImageIcons. For a single image, I would think about making a custom subclass of JPanel and overriding its paintComponent method to draw the image.
  3. (see 2)
Obsess answered 18/11, 2008 at 17:49 Comment(0)
N
6

JPanel is almost always the wrong class to subclass. Why wouldn't you subclass JComponent?

There is a slight problem with ImageIcon in that the constructor blocks reading the image. Not really a problem when loading from the application jar, but maybe if you're potentially reading over a network connection. There's plenty of AWT-era examples of using MediaTracker, ImageObserver and friends, even in the JDK demos.

Natatory answered 18/11, 2008 at 18:21 Comment(0)
J
6

I'm doing something very similar in a private project I'm working on. Thus far I've generated images up to 1024x1024 without any problems (except memory) and can display them very quickly and without any performance problems.

Overriding the paint method of JPanel subclass is overkill and requires more work than you need to do.

The way I do it is:

Class MapIcon implements Icon {...}

OR

Class MapIcon extends ImageIcon {...}

The code you use to generate the image will be in this class. I use a BufferedImage to draw onto then when the paintIcon() is called, use g.drawImvge(bufferedImage); This reduces the amount of flashing done while you generate your images, and you can thread it.

Next I extend JLabel:

Class MapLabel extends Scrollable, MouseMotionListener {...}

This is because I want to put my image on a scroll pane, I.e. display part of the image and have the user scroll around as needed.

So then I use a JScrollPane to hold the MapLabel, which contains only the MapIcon.

MapIcon map = new MapIcon (); 
MapLabel mapLabel = new MapLabel (map);
JScrollPane scrollPane = new JScrollPane();

scrollPane.getViewport ().add (mapLabel);

But for your scenario (just show the whole image every time). You need to add the MapLabel to the top JPanel, and make sure to size them all to the full size of the image (by overriding the GetPreferredSize()).

Jeopardous answered 18/11, 2008 at 18:28 Comment(0)
C
6

This answer is a complement to @shawalli's answer...

I wanted to reference an image within my jar too, but instead of having a BufferedImage, I simple did this:

 JPanel jPanel = new JPanel();      
 jPanel.add(new JLabel(new ImageIcon(getClass().getClassLoader().getResource("resource/images/polygon.jpg"))));
Cleric answered 30/9, 2015 at 17:10 Comment(0)
B
5

Create a source folder in your project directory, in this case I called it Images.

JFrame snakeFrame = new JFrame();
snakeFrame.setBounds(100, 200, 800, 800);
snakeFrame.setVisible(true);
snakeFrame.add(new JLabel(new ImageIcon("Images/Snake.png")));
snakeFrame.pack();
Baird answered 18/4, 2016 at 5:2 Comment(0)
C
5

You can avoid using own Components and SwingX library and ImageIO class:

File f = new File("hello.jpg");
JLabel imgLabel = new JLabel(new ImageIcon(file.getName()));
Clockwise answered 23/2, 2018 at 7:32 Comment(0)
D
2

I can see many answers, not really addressing the three questions of the OP.

1) A word on performance: byte arrays are likely unefficient unless you can use an exact pixel byte ordering which matches to your display adapters current resolution and color depth.

To achieve the best drawing performance, simply convert your image to a BufferedImage which is generated with a type corresponding to your current graphics configuration. See createCompatibleImage at https://docs.oracle.com/javase/tutorial/2d/images/drawonimage.html

These images will be automatically cached on the display card memory after drawing a few times without any programming effort (this is standard in Swing since Java 6), and therefore the actual drawing will take negligible amount of time - if you did not change the image.

Altering the image will come with an additional memory transfer between main memory and GPU memory - which is slow. Avoid "redrawing" the image into a BufferedImage therefore, avoid doing getPixel and setPixel at all means.

For example, if you are developing a game, instead of drawing all the game actors to a BufferedImage and then to a JPanel, it is a lot faster to load all actors as smaller BufferedImages, and draw them one by one in your JPanel code at their proper position - this way there is no additional data transfer between the main memory and GPU memory except of the initial transfer of the images for caching.

ImageIcon will use a BufferedImage under the hood - but basically allocating a BufferedImage with the proper graphics mode is the key, and there is no effort to do this right.

2) The usual way of doing this is to draw a BufferedImage in an overridden paintComponent method of the JPanel. Although Java supports a good amount of additional goodies such as buffer chains controlling VolatileImages cached in the GPU memory, there is no need to use any of these since Java 6 which does a reasonably good job without exposing all of these details of GPU acceleration.

Note that GPU acceleration may not work for certain operations, such as stretching translucent images.

3) Do not add. Just paint it as mentioned above:

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.drawImage(image, 0, 0, this); 
}

"Adding" makes sense if the image is part of the layout. If you need this as a background or foreground image filling the JPanel, just draw in paintComponent. If you prefer brewing a generic Swing component which can show your image, then it is the same story (you may use a JComponent and override its paintComponent method) - and then add this to your layout of GUI components.

4) How to convert the array to a Bufferedimage

Converting your byte arrays to PNG, then loading it is quite resource intensive. A better way is to convert your existing byte array to a BufferedImage.

For that: do not use for loops and copy pixels. That is very very slow. Instead:

  • learn the preferred byte structure of the BufferedImage (nowadays it is safe to assume RGB or RGBA, which is 4 bytes per pixel)
  • learn the scanline and scansize in use (e.g. you might have a 142 pixels wide image - but in the real life that will be stored as a 256 pixel wide byte array since it is faster to process that and mask the unused pixes by the GPU hardware)
  • then once you have an array build according to these principles, the setRGB array method of the BufferedImage can copy your array to the BufferedImage.
Dilly answered 10/3, 2018 at 0:36 Comment(0)

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